Bridged silver(I) complexes of the polycyclic aromatic compounds tetraphenylethylene and 1,1,4,4-tetraphenyl-1,3-butadiene

Article abstract of DOI:10.1021/ic000263u

For the purpose of investigating the coordination behavior of the sterically congested alkenes and exploring the possibility of cofacial complexation in the polycyclic aromatic system for formation of extended polymeric networks, tetraphenylethylene (tphe) and 1,1,4,4-tetraphenyl-1,3-butadiene (tphb) have been studied with regard to their complexation with a silver(I) ion. The crystal structures of [Ag(tphe)(ClO₄)(p-xylene)], [Ag₂(tphe)(ClO₄)₂], [Ag₄(tphe)(CF₃SO₃)₄], [Ag₂(tphb)(ClO₄)₂], and [Ag₂(tphb)(CF₃SO₃)₂], together with the metal-free ligands tphe and tphb, have been determined by single-crystal X-ray diffraction. The π-electron-rich cleft in organic components is found to offer a potential site for complexation, which can be utilized to generate an interesting array of organometallic compounds with one- and two-dimensional frameworks.

Full text of DOI:10.1021/ic000263u

5430
Inorg. Chem. 2000, 39, 5430-5436
Ar ticles
Bridged Silver(I) Complexes of the Polycyclic Aromatic Compounds Tetraphenylethylene
and 1,1,4,4-Tetraphenyl-1,3-butadiene
Ichiro Ino,† Liang Ping Wu,‡ Megumu Munakata,*,† Takayoshi Kuroda-Sowa,†
Masahiko Maekawa,† Yusaku Suenaga,† and Ryusuke Sakai†
Department of Chemistry, Kinki University, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan,
and East China Normal University, Shanghai 200062, China
ReceiVed March 7, 2000
For the purpose of investigating the coordination behavior of the sterically congested alkenes and exploring the
possibility of cofacial complexation in the polycyclic aromatic system for formation of extended polymeric networks,
tetraphenylethylene (tphe) and 1,1,4,4-tetraphenyl-1,3-butadiene (tphb) have been studied with regard to their
complexation with a silver(I) ion. The crystal structures of [Ag(tphe)(ClO4)(p-xylene)], [Ag2(tphe)(ClO4)2],
[Ag4(tphe)(CF3SO3)4], [Ag2(tphb)(ClO4)2], and [Ag2(tphb)(CF3SO3)2], together with the metal-free ligands tphe
and tphb, have been determined by single-crystal X-ray diffraction. The π-electron-rich cleft in organic components
is found to offer a potential site for complexation, which can be utilized to generate an interesting array of
organometallic compounds with one- and two-dimensional frameworks.
Introduction
naphtho[2,3-a]pyrene8 for their unique shape, size, and a number
of closely spaced molecular orbitals. These organic species
exhibit extraordinary abilities, combining good ligating property
and perfect planarity concurrently interacting with metal ions
above and below rings. We therefore wished to synthesize silver-
(I) complexes of phenylated alkenes to explore the possibility
of cofacial complexation of the cation-π complexes and to
examine any unusual coordination and reactivity which these
organic ligands might induce. For simplicity we have limited
our initial work to the synthesis of silver derivatives of
tetraphenylethylene (tphe) and 1,1,4,4-tetraphenyl-1,3-butadiene
(tphb). The results of our study are reported herein.
Transition-metal π complexes of polycyclic aromatic hydro-
carbons exhibit stereochemical features of exceptional interest;
examples are the conformational variability in silver complexes
of planar aromatic compounds with a vast range of open
frameworks and layered materials in which the ionic inorganic
species is occluded within an organic framework.1 It is the
overall planarity of the organic components and the extended
delocalized π system that have caused the current interest in
the elaboration of the synthetic chemistry of metal ion-aromatic
π-donor-acceptor complexes with possible applications in
electrical conductors and photosensitive devices.2-4
Experimental Section
Our interest in these compounds stems from the work
involving transition-metal derivatives of highly anellated arenes
such as pyrene,5 perylene,5 coronene,6 benzo[ghi]perylene,7 and
General Methods. All reactions and manipulations were carried out
under an argon atmosphere by using usual Schlenk techniques. Solvents
were dried and distilled by using standard methods prior to use. High-
purity argon was used to deoxygenate solvents. Reagent grade tphe
and tphb were purchased from Tokyo Chemical Industry Co., Ltd.,
whereas silver(I) perchlorate and silver(I) trifluoromethanesulfonate
were purchased from Aldrich. All other chemicals were purchased from
Wako Pure Chemical, Inc. and used as received. The IR spectra were
recorded as KBr disks on a JASCO FT-IR-8000 spectrometer, and ESR
spectra, on a JEOL JES-TE200 ESR spectrometer.
* To whom correspondence should be addressed. E-mail: munakata@
chem.kindai.ac.jp.
† Kinki University.
‡ East China Normal University.
(1) Munakata, M.; Wu, L. P.; Ning, G. L. Coord. Chem. ReV. 2000, 198,
171.
(2) Harvey, R. G. Polycyclic Aromatic Hydrocarbons; Wiley-VCH:
Weinheim, Germany, 1997.
(3) (a) Cram, D. C. Angew. Chem., Int. Ed. Engl. 1988, 27, 1009. (b)
Desiraju, G. R.; Gavezzotti, A. J. Chem. Soc., Chem. Commun. 1989,
621. (c) Diederich, F. Angew. Chem., Int. Ed. Engl. 1988, 27, 362.
(d) Fyfe, M. C. T.; Stoddart, J. F. Acc. Chem. Res. 1997, 30, 393.
(4) (a) Dias, J. R. Acc. Chem. Res. 1985, 18, 241. (b) Iuliucci, R. J.; Phung,
C. G.; Facelli, J. C.; Grant, D. M. J. Am. Chem. Soc. 1996, 118, 4880.
(c) Janke, R. H.; Haufe, G.; Wu¨rthwein, E.-U.; Borkent, J. H. J. Am.
Chem. Soc. 1996, 118, 6031. (d) Debad, J. D.; Morris, J. C.; Lynch,
V.; Magnus, P.; Bard, A. J. J. Am. Chem. Soc. 1996, 118, 2374. (e)
Scott, L. T.; Bratcher, M. S.; Hagen, S. J. Am. Chem. Soc. 1996, 118,
8743. (f) Schulman, J. M.; Disch, R. L. J. Am. Chem. Soc. 1996, 118,
8470. (g) Morgenroth, F.; Ku¨bel, C.; Mu¨llen, K. J. Mater. Chem. 1997,
7, 1207. (h) Pozniak, B. P.; Dunbar, R. C. J. Am. Chem. Soc. 1997,
119, 10439. (i) Laali, K. K.; Houser, J. J. J. Chem. Soc., Perkin Trans.
2 1994, 1303. (j) Cioslowski, J.; Liu, G.; Martinov, M.; Piskorz, P.;
Moncrieff, D. J. Am. Chem. Soc. 1996, 118, 5261. (k) Veiros, L. F.;
Calhorda, M. J.; Canadell, E. Inorg. Chem. 1994, 33, 4290. (l)
Freedman, D. A.; Matachek, J. R.; Mann, K. R. Inorg. Chem. 1993,
32, 1078.
(5) Munakata, M.; Wu, L. P.; Kuroda-Sowa, T.; Maekawa, M.; Suenaga,
Y.; Sugimoto, K. Inorg. Chem. 1997, 36, 4903.
(6) Munakata, M.; Wu, L. P.; Kuroda-Sowa, T.; Maekawa, M.; Suenaga,
Y.; Ning, G. L.; Kojima, T. J. Am. Chem. Soc. 1998, 120, 8610.
(7) Munakata, M.; Wu, L. P.; Ning, G. L.; Kuroda-Sowa, T.; Maekawa,
M.; Suenaga, Y.; Maeno, N. J. Am. Chem. Soc. 1999, 121, 4968.
(8) Ning, G. L.; Wu, L. P.; Sugimoto, K.; Munakata, M.; Kuroda-Sowa,
T.; Maekawa, M. J. Chem. Soc., Dalton Trans. 1999, 2529.
10.1021/ic000263u CCC: $19.00 © 2000 American Chemical Society
Published on Web 11/04/2000

Bridged Silver(I) Polycyclic Aromatic Compounds
Inorganic Chemistry, Vol. 39, No. 24, 2000 5431
Table 1. Crystallographic Data for tphe, tphb, and Complexes 1-5
tphe
tphb
1
2
3
4
5
formula
fw
space
group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
C26H20
332.44
P21
C28H22
358.48
P1
C34H30AgClO4
645.93
P21/n
C26H20Ag2Cl2O8
747.08
Pccn
C30H20Ag4S4F12O12
1360.17
C2/c
C28H22Ag2Cl2O8
773.12
P1
C30H22Ag2S2F6O6
872.35
C2/c
9.8234(8)
9.5014(9)
10.7065(3)
10.110(1)
10.851(2)
9.820(2)
103.64(1)
94.95(1)
99.31(1)
1024.3(3)
2
12.345(3)
9.253(3)
25.376(1)
18.7791(6)
9.322(2)
14.8669(1)
20.527(5)
10.028(1)
18.905(1)
8.220(2)
8.9164(2)
10.396(2)
108.185(2)
93.824(2)
112.033(5)
656.3(2)
1
19.534(2)
5.0005(7)
30.962(1)
107.0892(9)
98.719(1)
94.257(1)
91.861(1)
955.2(1)
2
2865.2(8)
4
2602.5(4)
4
3880.8(8)
4
3022.8(5)
4
T, °C
λ(Mo KR),
Å
22
0.71069
23
0.71069
22
0.71069
22
0.71069
22
0.71069
22
0.71069
-150
0.71069
F, g/cm3
1.156
0.65
0.050
0.161
1.162
0.65
0.047
0.138
1.497
8.32
0.055
0.090
1.907
17.55
0.055
0.166
2.328
23.17
0.064
0.162
1.956
17.43
0.035
0.068
1.917
15.11
0.036
0.10
µ, cm-1
a
R1
b
wR2
a ∑(|Fo| - |Fc|)/∑|Fo|. b [∑w(Fo - Fc2)2/∑w(Fo )2]1/2
.
2
2
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(tphe)(ClO4)(p-xylene)] (1). To a p-xylene solution
(5 mL) containing silver perchlorate (20.7 mg, 0.1 mmol) was added
tphe (33.2 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. The glass tube, sealed under Ar and wrapped with
aluminum foil, was left standing at room temperature for 2 weeks;
colorless brick crystals of 1 were obtained (30 mg, 46%). Anal. Calcd
for C30H25AgClO4 (the formula with half solvent molecule): C, 60.78;
H, 4.22. Found: C, 60.54; H, 4.20. Main IR bands (cm-1): 3070(m),
1956(w), 1888(w), 1599(m), 1480(s), 1442(s), 1111(s), 680(s), 626-
(s).
[Ag2(tphe)(ClO4)2] (2). This compound was synthesized in a manner
similar to that for 1 with 1,3,5-trimethylbenzene in place of p-xylene
as the solvent. The yield was 43% (16 mg). Anal. Calcd for C26H20-
Ag2Cl2O8: C, 41.76; H, 2.68. Found: C, 41.72; H, 2.71. Main IR bands
(cm-1): 3074(m), 2015(w), 1956(w), 1597(m), 1486(s), 1442(s), 1118-
(s), 690(s), 630(s).
[Ag4(tphe)(CF3SO3)4] (3). To a 1,3,5-trimethylbenzene solution (10
mL) containing silver trifluoromethanesulfonate (51.4 mg, 0.2 mmol)
was added tphe (33.2 mg, 0.1 mmol). The mixture was stirred for 10
min and filtered. A portion of the filtrate (3 mL) was transferred to a
glass tube and layered with n-hexane as a diffusion solvent. The glass
tube, sealed under Ar and wrapped with Al-foil, was left standing at
room temperature for 2 weeks; colorless brick crystals of 3 were
obtained (31 mg, 46%). Anal. Calcd for C30H20Ag4S4F12O12: C, 26.49;
H, 1.47. Found: C, 26.53; H, 1.48. Main IR bands (cm-1): 3076(m),
1956(w), 1894(w), 1599(m), 1480(s), 1442(s), 1269(s), 1182(s), 1035-
(s), 695(s), 636(s).
[Ag2(tphb)(ClO4)2] (4). To a solution of tphb (17.9 mg, 0.05 mmol)
in 5 mL of 1,3,5-trimethylbenzene was added 20.7 mg of silver
perchlorate (0.1 mmol). The mixture was stirred and filtered. A portion
of the filtrate (3 mL) was transferred to a 7 mm diameter glass tube
and layered with 3 mL of n-hexane as a diffusion solvent. The tube
was sealed under Ar and wrapped with Al-foil, and after standing for
2 weeks at room temperature, yellow plate crystals of 4 were obtained
(18 mg, 47%). Anal. Calcd for C28H22Ag2Cl2O8: C, 43.50; H, 2.85.
Found: C, 43.21; H, 2.56. Main IR bands (cm-1): 3053(m), 1597(m),
1478(m), 1350(m), 1107(s), 730(s), 628(s).
[Ag2(tphb)(CF3SO3)2] (5). Yellow needle single crystals of 5 were
synthesized in a manner similar to that for 4 with silver triflate in place
of silver perchlorate. The yield was 60% (26 mg). Anal. Calcd for
C30H22Ag2S2F6O6: C, 41.30; H, 2.52. Found: C, 41.04; H, 2.52. Main
IR bands (cm-1): 3053(m), 1599(m), 1436(w), 1352(m), 1265(s), 1142-
(s), 1035(s), 698(s), 642(s).
X-ray Data Collection and Structure Solutions and Refinements.
A suitable single crystal was mounted on a glass fiber, and diffraction
data were collected at -150 °C for 5 and at room temperature for the
rest on a Quantum charge-coupled device area detector coupled with a
Rigaku AFC7 diffractometer with graphite monochromated Mo KR
radiation. The ω/2θ scan mode was employed, and stationary back-
ground counts were recorded on each side of the reflection, the ratio
of peak counting time vs background counting time being 2:1. Weak
reflections (I < 10.0σ(I)) were rescanned up to three times and counts
accumulated to improve counting statistics. The intensities of three
reflections were monitored regularly after measurement of 150 reflec-
tions and indicated crystal stability in all cases. Azimuthal scans of
several reflections for each compound indicated no need for an
absorption correction. All intensity data were corrected for Lorentz
polarization effects.
The structures were solved by direct methods (MITHRIL9) followed
by subsequent Fourier-difference calculation and refined by a full-matrix
least-squares analysis on F2, using the TEXSAN package.10 All of the
full-occupancy non-hydrogen atoms were refined anisotropically.
Hydrogen atoms of all of the structures were introduced in their
calculated positions; they were included, but not refined, in the
refinement. The counteranions ClO4- were found to have high thermal
motions in 1, 2, and 4. 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.
Results
Crystal Structures of tphe and tphb. To gain an insight
into cation-π interactions, the crystal structures of the metal-
free ligands tphe and tphb were determined by X-ray analysis.
Single crystals for both compounds were obtained by recrys-
tallization of the sample in n-pentane. The infrared bands of
tphe appear at 3074 cm-1 (νC-H) and 1498 cm-1 (νCdC), whereas
the corresponding bands for tphb fall into 3078 and 1450 cm-1
,
respectively. Structure determination revealed that tphe possesses
two sets of face-to-face or cofacial benzene rings around the
central CdC bond, with dihedral angles between phenyl groups
of 54.84 and 55.58°. For tphb, all of the four phenyl rings are
twisted against the plane defined by the butadiene moiety with
dihedral angles of 43.1, 47.3, 47.5, and 48.5°. We do not deal
with any detailed structures here because their structural data
are presented as Supporting Information. However, these
(9) Gilmore, C. J. J. Appl. Crystallogr. 1984, 17, 42.
(10) TEXSAN-TEXRAY, Structural Analysis Package; Molecular Structure
Corp.: The Woodlands, TX, 1985 and 1999.

5432 Inorganic Chemistry, Vol. 39, No. 24, 2000
Ino et al.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
Complexes 1-5
complex 1
Ag-O(1)
Ag-C(3)
Ag-C(27)
2.394(7) Ag-C(2)
2.702(6) Ag-C(15)
2.533(6) Ag-C(28)
2.519(5)
2.602(5)
2.571(5)
O(1)-Ag-C(2) 115.4(3)
O(1)-Ag-C(15) 83.2(3)
O(1)-Ag-C(3)
O(1)-Ag-C(27)
C(2)-Ag-C(3)
C(2)-Ag-C(27)
C(3)-Ag-C(15)
C(3)-Ag-C(28)
C(15)-Ag-C(28)
87.8(3)
100.5(2)
30.5(2)
108.8(2)
137.1(2)
122.8(2)
96.9(2)
O(1)-Ag-C(28) 122.3(2)
C(2)-Ag-C(15) 124.1(2)
C(2)-Ag-C(28) 111.6(2)
C(3)-Ag-C(27) 103.7(2)
C(15)-Ag-C(27) 119.2(2)
C(27)-Ag-C(28)
31.4(2)
complex 2
Ag-O(1)
Ag-C(1)
Ag-C(13)
2.389(6)
2.672(4)
2.506(5)
Ag-O(3)
Ag-C(2)
2.536(8)
2.464(5)
Figure 1. Molecular structure and atom numbering of 1.
features are crucial in determining the overall structures of their
metal complexes as presented below.
O(1)-Ag-O(3)
C(1)-Ag-C(2)
O(3)-Ag-C(1)
O(3)-Ag-C(13)
C(1)-Ag-C(13)
78.6(2)
114.6(2)
113.7(1)
106.6(2)
107.9(2)
O(1)-Ag-C(1)
O(1)-Ag-C(13)
O(3)-Ag-C(2)
C(1)-Ag-C(2)
C(2)-Ag-C(13)
144.4(2)
99.3(2)
106.9(2)
30.9(1)
Characterization of the tphe Complexes 1, 2, and 3. Silver-
(I) complexes of tphes1, 2, and 3swere prepared by the
reaction of the appropriate starting material, AgClO4 or AgCF3-
SO3, with tphe in p-xylene or 1,3,5-trimethylbenzene. All of
the complexes were air-stable white crystals and found to be
mildly light sensitive as solids and more sensitive in solution,
thus samples were stored in the aluminum foil wrapped
containers in a freezer.
135.9(2)
Complex 3
Ag(1)-O(1)
Ag(1)-O(4)
Ag(1)-C(2)
Ag(2)-O(2)
Ag(2)-O(4)
Ag(2)-C(8)
2.343(4) Ag(1)-O(3)
2.470(5) Ag(1)-O(5)
2.493(5) Ag(1)-C(2)
2.375(4) Ag(2)-O(3)
2.521(5) Ag(2)-O(6)
2.571(5) Ag(2)-C(9)
2.573(5)
2.570(4)
2.481(6)
2.587(5)
2.498(4)
2.442(6)
The crystallographic studies revealed that 1 exists in the solid
state as a simple mononuclear complex, albeit one with some
unusual features. An ORTEP drawing of 1 with the atom
numbering scheme is shown in Figure 1, which shows the
tetrahedrally coordinated Ag(I) ion bonded to one tphe moiety,
one p-xylene solvent molecule, and one perchlorate anion. The
tphe interacts with the metal center in an η1/η2 fashion, and as
anticipated, the silver ion is found in the cleft between the two
phenyl rings, at Ag-C distances of 2.602(5), 2.519(5), and
2.702(6) Å, respectively. The coordination of p-xylene deserves
some comment. Previously, the coordination of silver(I) toward
m-xylene and o-xylene was reported by Amma and co-
workers,11,12 and both complexes are found to be reasonably
stable in the air and show an oxygen-bridged dimeric structure
of bis(xylene)silver perchlorate. This work presents the first
example of p-xylene coordinated to a metal ion in an η2, rather
than η1, fashion as observed in the m- or o-xylene system.
Although the Ag-C distances of 2.533(6) and 2.571(5) Å found
in p-xylene are comparable with those in the other two xylene
complexes, it should be noted that the coordinated p-xylene
entities are gradually liberated in the absence of sufficient
solvent vapor pressure primarily because of the volatility of the
solvent. This gives rise to a little deviation of the elemental
analysis from the calculated data (in fact, the measured C and
H percentages are consistent with the calculated data on the
basis of the formula having half of the p-xylene molecules).
By using 1,3,5-trimethylbenzene to replace p-xylene in the
above reaction, a polynuclear complex 2 was isolated, whose
molecular structure is given in Figure 2. In contrast with the
coordination of p-xylene in 1, the solvent molecule 1,3,5-
trimethylbenzene does not have effective interaction with the
metal ion in 2 presumably because of the three bulky methyl
groups that block the metal ion from approaching the π electrons
of the benzene rings. The structure of 2 features an ionic sheet
O(1)-Ag(1)-O(3) 128.2(2)
O(1)-Ag(1)-O(5) 86.0(2)
O(1)-Ag(1)-C(2) 129.6(2)
73.1(1)
O(3)-Ag(1)-C(2) 101.6(2)
O(4)-Ag(1)-C(1) 135.7(2)
O(1)-Ag(1)-O(4)
81.5(1)
O(1)-Ag(1)-C(1) 134.5(2)
O(3)-Ag(1)-O(4)
O(3)-Ag(1)-C(1)
75.2(2)
92.0(2)
O(3)-Ag(1)-O(5)
O(4)-Ag(1)-O(5) 126.9(2)
O(4)-Ag(1)-C(2) 107.6(2)
O(5)-Ag(1)-C(2) 119.8(2)
O(2)-Ag(2)-O(3) 129.0(1)
O(5)-Ag(1)-C(1)
C(1)-Ag(1)-C(2)
O(2)-Ag(2)-O(4)
86.9(2)
32.8(2)
81.9(2)
O(2)-Ag(2)-O(6)
82.3(2)
O(2)-Ag(2)-C(8) 123.2(2)
O(2)-Ag(2)-C(9) 130.0(2)
O(3)-Ag(2)-O(4)
74.1(2)
O(3)-Ag(2)-O(6)
O(3)-Ag(2)-C(9)
80.4(1)
98.7(2)
O(3)-Ag(2)-C(8) 105.9(1)
O(4)-Ag(2)-O(6) 130.4(2)
O(4)-Ag(2)-C(9) 131.5(2)
O(4)-Ag(2)-C(8) 102.7(2)
O(6)-Ag(2)-C(8) 125.1(2)
O(6)-Ag(2)-C(9)
93.5(2)
C(8)-Ag(2)-C(9)
31.8(2)
complex 4
Ag-O(1)
Ag-C(1)
Ag-C(10)
2.358(3) Ag-O(1′)
2.551(3) Ag-C(2)
2.526(3) Ag-C(11)
2.489(3)
2.447(3)
2.626(3)
O(1)-Ag-O(1′)
71.0(1)
O(1)-Ag-C(1)
112.3(1)
113.8(1)
121.8(1)
83.8(1)
32.72(9)
101.71(10)
98.8(1)
O(1)-Ag-C(2) 106.0(1)
O(1)-Ag-C(11) 145.2(1)
O(1′)-Ag-C(2) 152.6(1)
O(1)-Ag-C(10)
O(1′)-Ag-C(1)
O(1′)-Ag-C(10)
C(1)-Ag-C(2)
C(1)-Ag-C(11)
O(1′)-Ag-C(11)
97.3(1)
C(1)-Ag-C(10) 132.59(9)
C(2)-Ag-C(10) 120.48(10) C(2)-Ag-C(11)
C(10)-Ag-C(11)
31.46(10)
complex 5
Ag-O(1)
Ag-O(3)
Ag-C(5)
2.418(3)
2.503(3)
2.413(3)
Ag-O(2)
Ag-O(3′)
Ag-C(6)
2.417(3)
2.524(3)
2.598(4)
O(1)-Ag-O(2)
O(1)-Ag-O(3′)
O(1)-Ag-C(6)
O(2)-Ag-O(3′)
O(2)-Ag-C(6)
O(3)-Ag-C(5)
O(3′)-Ag-C(5)
C(5)-Ag-C(6)
83.36(9)
128.33(9)
132.2(1)
80.61(9)
95.6(1)
101.8(1)
106.7(1)
32.1(1)
O(1)-Ag-O(3)
O(1)-Ag-C(5)
O(2)-Ag-O(3)
O(2)-Ag-C(5)
O(3)-Ag-O(3′)
O(3)-Ag-C(6)
O(3′)-Ag-C(6)
78.22(9)
121.9(1)
130.07(9)
127.1(1)
75.7(1)
130.6(1)
98.2(1)
(11) Taylor, I. F., Jr.; Hall, E. A.; Amma, E. L. J. Am. Chem. Soc. 1969,
91, 5745.
(12) Taylor, I. F., Jr.; Amma, E. L. Chem. Commun. 1970, 1442.

Bridged Silver(I) Polycyclic Aromatic Compounds
Inorganic Chemistry, Vol. 39, No. 24, 2000 5433
Figure 2. Molecular structure and atom numbering of 2.
Figure 4. Molecular structure and atom numbering of 3.
Figure 3. Two-dimensional sheet structure and the schematic view of
2.
made up of Ag-OClO2O-Ag chains separated by the aromatic
groups as shown in Figure 3. The zigzag chains may be viewed
-
as an alternating tetrahedral of the ClO4 ions and the four-
Figure 5. Two-dimensional sheet structure and the schematic view of
3.
coordinate Ag(I) ion sharing a common oxygen vertex, propa-
gating along the a axis. Each aromatic group bridges two
adjacent ionic chains by chelating one Ag in each cleft, giving
a two-dimensional sheet network. Each silver atom acquires its
usual coordination number of four by forming bonds with the
π orbitals of two η1/η2 phenyl groups and two oxygen atoms
of the different perchlorate anions. The Ag-C bond distances
and bond angles are normal, Table 2, which do not deserve
further comment.
Complex 3 was synthesized by the similar reaction to that
for 2, with AgCF3SO3 in place of AgClO4 as the starting
material. As in 2, 1,3,5-trimethylbenzene is not involved in
coordination with the metal ion. Despite similar reaction
conditions and the same solvent employed, these two complexes
exhibit significantly different crystallographic and structural
features originated from the different bonding nature of the
counterions. In 3, there exist two crystallographically indepen-
dent Ag(I) ions, Figure 4. The ionic sheet made up of Ag-
CF3SO3-Ag chains is still maintained, in which the triflate ions
involve an unusual tetradentate bonding fashion linking four
metal ions, with Ag-O bond lengths ranging from 2.343(4) to
2.587(5) Å. Each silver atom in turn is coordinated to one phenyl
group of the organic ligand and one oxygen atom of the four
different tetradentate CF3SO3- ions in a distorted square pyramid
geometry, with four oxygen atoms forming the base plane and
the π interaction occupying the apex position. As a result, the
Ag(1) and Ag(2) ions are bridged by four triflates to give a
dinuclear unit with an Ag‚‚‚Ag separation of 3.284 Å, Figure
5. Complex 3 is unusual in the sense that each tphe is interacting
with four metal centers with each phenyl group η2-bonded to
one metal ion, rather than cofacially binding the metal center
in the cleft as observed in 1 and 2.
IR spectroscopy indicated the presence of the appropriate
counterion and the presence of ligands within the complexes.
Typically, aromatic hydrocarbons in their transition-metal com-
plexes can form charge-transfer species or even organic radicals
depending on the degree of charge transfer in the ground state.
At room temperature, no strong ESR spectrum was observed
for 1 and 2. On the contrary, 3 exhibited a well-resolved intense
resonance at g ) 2.0063, typical of aromatic hydrocarbon
radicals.13 However, the spin density for the organic radicals,
estimated from the comparison with the DPPH (diphenylpic-
(13) (a) Davies, A. G.; McGuchan, D. C. Organometallics 1991, 10, 329.
(b) Courtneidge, J. L.; Davies, A. G. Acc. Chem. Res. 1987, 20, 90.
(c) Davies, A. G.; Shields, C. J. Chem. Soc., Perkin Trans. 2 1989,
1001.

5434 Inorganic Chemistry, Vol. 39, No. 24, 2000
Ino et al.
Figure 6. Molecular structure (a) and perspective view of infinite chain
structure (b) in 4. Noncoordinating oxygen atoms of the perchlorate
ions are omitted for clarity.
rylhydrazyl) standard, was less than 0.1%, so low that the ESR
signal could be easily associated with an impurity. The attri-
bution of the observed ESR signal is not immediately known.
Characterization of the tphb Complexes 4 and 5. Silver-
(I) complexes of tphb, 4 and 5, were prepared by the reaction
of tphb with 2 molar equiv of appropriate metal salt in 1,3,5-
trimethylbenzene. Compounds 4 and 5 were both air stable
yellow crystals and mildly light sensitive in the solid state. IR
spectroscopy indicated the presence of the appropriate counte-
rion and the presence of ligands within the complexes. At room
temperature, no strong ESR spectrum was observed in either
case.
Figure 7. Molecular structure (a), perspective view of two-dimensional
sheet structure (b), and the schematic view (c) in 5.
The crystallographic studies revealed that complex 4 exists
in the solid state as a one-dimensional polymer of silver(I)
dimers. Figure 6 depicts a perspective view with atom number-
Discussion
-
ing of the molecule. Each ClO4 anion bridges between two
Silver(I) complexes of tphe and tphb are easily prepared
without elaborate syntheses, suggesting that the cation-π
interactions are favorable in most cases. However, the reactivity
and the topology of the ensuing coordination networks are found
to depend strongly on the counterion, solvent, and ligand
geometry.14 Thus, understanding how these considerations affect
metal coordination and influence crystal packing is at the heart
of controlling coordination network assembly.
We have systematically studied the reactivity of silver(I) salts
with tphe in different solvents. Benzene and its methyl-
substituted species have long been suggested as the ideal media
for preparation of the silver(I)-π complexes.1,5-8,11,12 However,
our attempt to obtain silver(I) complexes of tphe in benzene or
toluene failed because of the competitive complexation of the
solvent molecule to Ag(I) ions over tphe.15 When such a reaction
was carried out in p-xylene as discussed in the Experimental
Section, a mononuclear 1:1 metal-to-tphe complex of 1 was
isolated, which includes weakly bound solvent molecule. To
explore the coordination network based on the ionic species
and the sterically congested alkenes without involvement of the
metal centers at Ag-O distances of 2.358(3) and 2.489(3) Å.
The double-bridged dinuclear core Ag2O2 is thus formed with
an Ag‚‚‚Ag separation of 3.946 Å. The polyhedron of metal
coordination is completed to four by further interaction with π
electrons of one phenyl group of two different tphb entities; in
other words, each ligand group bridges between two adjacent
ionic dinuclear cores with each phenyl ring η2-interacting with
one metal center, giving rise to an alternate Ag2O2-aromatic-
Ag2O2 sequential arrangement running along the c axis.
Figure 7 indicates a portion of the molecular structure of 5,
in which each silver(I) ion is coordinated to one oxygen atom
of four separate triflates and one phenyl group of the tphb in a
distorted square-based pyramidal geometry. As observed in 3,
each triflate ion is bonded to four metal centers, with Ag-O
bond lengths ranging from 2.417(3) to 2.524(3) Å. The four O
atoms defining the basal plane around the Ag ion deviates
significantly from the mean plane by 0.28 Å. The apical
coordination site is occupied by π electrons from one phenyl
ring of the tphb at Ag-C bond distances of 2.413(3) and 2.598-
(4) Å. Each tphb group uses only two of its four phenyl rings
to link the nearby ionic chains, leading to a two-dimensional
array of the metal ions. It is interesting to note that the two
phenyl groups bound to Ag are almost coplanar to the butadiene
moiety.
(14) Janiak, C.; Uehlin, L.; Wu, H.-P.; Klu¨fers, P.; Piotrowski, H.;
Scharmann, T. G. J. Chem. Soc., Dalton Trans. 1999, 3121.
(15) Strauss, S. H.; Noirot, M. D.; Anderson, O. P. Inorg. Chem. 1985,
24, 4307.

Bridged Silver(I) Polycyclic Aromatic Compounds
Inorganic Chemistry, Vol. 39, No. 24, 2000 5435
Scheme 1
Figure 8. Tetradentate bridging of four Ag ions by one triflate in 3
and 5 and created channel network consisting of inner squares and outer
octagons.
Scheme 2
solvent molecule, 1,3,5-trimethylbenzene was selected as the
reaction media in the preparation of 2-5. As we had proposed,
1,3,5-trimethylbenzene did not coordinate to Ag(I) because of
the steric hindrance of the methyl groups, and the synthesized
products turned out to be our expected alkene-based polymeric
organometallic compounds. We infer from this result that the
cation-π interaction in silver-tphe and silver-tphb systems
is quite weak, and the related reactivity in solution is solvent
dependent.
From the examples given, it becomes clear that large
-
coordinating oxyanions such as NO3-, ClO4-, and CF3SO3
play a crucial role in stabilizing the silver(I) complexes and in
the construction of the extended polynuclear system.1,16-19 In
this work, silver perchlorate and silver triflate feature promi-
nently as ionic chains or columns in silver-π networks, and in
particular, the perchlorate coordinates in a variety of ways to
the silver, such as terminal bonding to one metal as observed
in 1 or bridging two metal centers by two or even one oxygen
atom of the ion in 2 and 4. The bonding diversity of the
counterion leads to the final products as, respectively, a simple
mononuclear, two-dimensional sheet, and one-dimensional
infinite chain structures with different stoichiometries.
formation of such an ionic channel network may have profound
influence on the stability of the synthesized products and on
the packing of the organic components with particular confor-
mation.
We have also used the triflate ion to argue the importance of
a counterion in building silver-π frameworks. Among the silver
salts in hand, AgCF3SO3 is the most accessible, safe, and stable.
The coordinative properties of the triflate ions have been
reviewed.20 The inertness and low nucleophilicity of the anion
suggest that it can have a useful role as both indifferent anions
and a relatively labile leaving group in inorganic chemistry.
Apart from the purely ionic state there are several possible
The final structures resulting from connection of the ionic
chains by the aromatic groups also strongly depends on the
detailed geometry and conformation of the hydrocarbons.
Despite intensive interest in cation-π interactions, only very
few π complexes of the sterically congested alkenes have been
reported in the literature.21 In previous studies of the silver(I)
complexes of aromatics, attention was devoted to the planar,1,5-7
nonplanar,22 and linear hydrocarbons.8 They feature two aro-
matic planes sandwiching the ionic chain on both sides resulting
in layered structures or act as linear bidentate ligands interacting
with metal ions alternately in an infinite-chain fashion. In this
work, we have examined the coordination chemistry of the
phenylated alkenes. In sharp contrast with our recently reported
silver(I) complex of 2,5-norbornadiene in which the aromatic
moiety interacts with two metal centers via two double bonds
of the olefin,22 the complexation of the central double bond is
found to be prevented in tphe because of the steric hindrance
of the four phenyl groups despite the expectation that it should
be normally regarded as a preferred site of interaction. Schemes
2 and 3 illustrate the complexation sites and the least-squares
plane calculation of tphe and tphb observed in complexes 1-5.
-
modes of bonding available to CF3SO3 in related silver(I)
complexes, Scheme 1. It often acts as an uncoordinated or
unidentate group,17 but sometimes shows bidentate behavior.18,19
The tridentate bridging of the triflate ion is rare but occurred in
the silver(I) complex of naphtho[2,3-a]pyrene.8 This work
presents the first example of a silver(I) complex involving
tetradentate-bridging triflate ions. The average Ag-O bond
distances of 2.49 and 2.47 Å found in 3 and 5, respectively,
are normal and comparable with the documented data.8,17-19
-
The remarkable feature of the tetradentate bonding of CF3SO3
observed in this work is that the ionic column of Ag-SO3
generates an extended channel network consisting of alternating
inner squares and outer octagons as shown in Figure 8. The
(16) Wu, H.-P.; Janiak, C.; Rheinwald, G.; Lang, H. J. Chem. Soc., Dalton
Trans. 1999, 183.
(17) Wu, L. P.; Dai, J.; Munakata, M.; Kuroda-Sowa, T.; Maekawa, M.;
Suenaga, Y.; Ohno, Y. J. Chem. Soc., Dalton Trans. 1998, 3255.
(18) Munakata, M.; Wu, L. P.; Kuroda-Sowa, T.; Maekawa, M.; Suenaga,
Y.; Sugimoto, K.; Ino, I. J. Chem. Soc., Dalton Trans. 1999, 373.
(19) Ning, G. L.; Munakata, M.; Wu, L. P.; Maekawa, M.; Suenaga, Y.;
Kuroda-Sowa, T.; Sugimoto, K. Inorg. Chem. 1999, 38, 5668.
(20) Lawrance, G. A. Chem. ReV. 1986, 86, 17.
(21) Gano, J. E.; Subramaniam, G.; Birnbaum, R. J. Org. Chem. 1990, 55,
4760.
(22) Munakata, M.; Wu, L. P.; Sugimoto, K.; Kuroda-Sowa, T.; Maekawa,
M.; Suenaga, Y.; Maeno, N.; Fujita, M. Inorg. Chem. 1999, 38, 5674.

5436 Inorganic Chemistry, Vol. 39, No. 24, 2000
Ino et al.
Scheme 3
with the silver atom. A similar case was observed in the tphb
complexes 4 and 5, where each benzene ring π-interacts with
one metal ion, and the dihedral angles between the butadiene
and phenyl groups also differ significantly from those of the
free ligand. This result is important in that it suggests that the
π-electron-rich clefts in both tphe and tphb offer several
complexation sites depending upon the countrions employed.
Conclusions
This work was part of the general research effort aimed at
extending the range of cation-π complexes by (i) designing
and using new hydrocarbons, (ii) altering the reaction media,
and (iii) changing the nature of the counterion in the organic/
inorganic hybrid networks. To establish whether the phenylated
alkenes tphe and tphb did adopt extended frameworks as we
had proposed, single-crystal X-ray diffraction studies were
undertaken on certain examples. The structural characterization
of five unprecedented organosilver(I) complexes shows that both
organic compounds bind the metal ion through phenyl-π
interactions rather than the olefin moiety. It also demonstrates
the consequences of bringing aromatic rings into close range
upon complexation of metal ions, that is, the extreme coordi-
native flexibility and variety. Nevertheless, the precise structural
features of the cation-π complexes formed are subtly dependent
upon the ligand geometry and the conformation, solvent, and
nature of the anion used. This finding is an interesting parallel
to the recently reported coordination chemistry of silver(I)
toward nitrogen donor ligands.14,16
In fact, both tphe and tphb can offer opportunities for a wide
variety of donor-acceptor interactions by twisting the benzene
rings around the central CdC bond(s). They feature four
equivalent benzene rings mutually or individually inclined to
approach the metal centers. The least-squares plane calculation
indicates that half of the tphe moiety is twisted against the other
by 10.10° for the metal-free ligand. As the number of benzene
rings bound to Ag increases from 1 to 3, the CdC twisting
angles decreases to 8.35, 4.73, and 4.49°, respectively. The
dihedral angles between phenyl groups in 1 (53.46 and 57.92°)
and 2 (52.15°) are only slightly changed compared with the
corresponding angles of 54.84 and 55.58° observed in the
coordination-free tphe, indicating that the cleft formed by the
two benzene rings in tphe is sterically suitable for chelating
one metal ion. By contrast, the two dihedral angles of the tphe
differ widely in 3 because of the absence of a cofacial interaction
Acknowledgment. This work was partially supported by a
Grant-in-Aid for Science Research [Nos. 09554041, 10440201,
and 10016743 (priority areas “Metal-assembled Complexes”)]
from the Ministry of Education, Science, Culture, and Sports
in Japan.
Supporting Information Available: X-ray crystallographic files,
in CIF format, for the structure determination of tphe, tphb, and
1-5. This material is available free of charge via the Internet at
http://pubs.acs.org.
IC000263U