A zigzag chain coordination polymer consisting of silver(I) ion having square planar geometry

Article abstract of DOI:10.1016/S0020-1693(01)00719-8

Silver(I) complexes of hexakis(tolylsulfanyl)benzene (htsb), [Ag(htsb)](PF₆) (1), have been prepared and their molecular structures were determined by X-ray crystallography. In 1, the silver ion prefers a square planar coordination geometry comprized of four S atoms from two different htsb molecules and producing a zigzag chain structure of Ag-S in the silver coordination polymer. Based on the thermo-gravimetry analysis results, two tolylsulfanyl groups were easily eliminated at approximately 211°C. However, [Ag(htsb)(2-butanone)] (PF₆) (2), which were obtained by the reactions in different solvents, showed a different colors and thermal degradation behaviors.

Full text of DOI:10.1016/S0020-1693(01)00719-8

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Inorganica Chimica Acta 328 (2002) 105–110
A zigzag chain coordination polymer consisting of silver(I) ion
having square planar geometry
Yusaku Suenaga a,*, Kouzou Kitamura a, Takayoshi Kuroda-Sowa a,
Masahiko Maekawa b, Megumu Munakata a
a Department of Chemistry, Kinki Uni6ersity, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
b Research Institute for Science and Technology, Kinki Uni6ersity, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
Received 20 June 2001; accepted 24 September 2001
Abstract
Silver(I) complexes of hexakis(tolylsulfanyl)benzene (htsb), [Ag(htsb)](PF6) (1), have been prepared and their molecular
structures were determined by X-ray crystallography. In 1, the silver ion prefers a square planar coordination geometry comprized
of four S atoms from two different htsb molecules and producing a zigzag chain structure of AgꢀS in the silver coordination
polymer. Based on the thermo-gravimetry analysis results, two tolylsulfanyl groups were easily eliminated at approximately
211 °C. However, [Ag(htsb)(2-butanone)] (PF6) (2), which were obtained by the reactions in different solvents, showed a different
colors and thermal degradation behaviors. © 2002 Elsevier Science B.V. All rights reserved.
Keywords: Silver(I) complexes; Square planar geometry; One-dimensional structure; Thermal degradation behavior
cyclic ligands have been interesting due to the stabiliza-
tion of unusual oxidation states. For these ligands
having macrocyclic nitrogen-containing unsaturated
heterocycles such as 5,5,7,12,12,14-hexamethyl-1,4,8,11-
tetraazacyclotetradecane [3], the silver(II) formed a
square planar geometry.
The coordination complexes of thioether ligands with
the d10 silver(I) ion are mainly restricted to macrocyclic
thioethers [4] in previous studies. Recently, we have
been exploring ways to modify the substituents to tailor
the polymer structures with silver(I)/poly(phenylsul-
fanyl)-substituted aromatic systems, which are well
known for their host–guest chemistry in the solid state
[5], as to the mode of polymerization, dimensionality
and framework
In this paper, we report the silver(I) coordination
polymer with a zigzag chain structure, in which silver(I)
ions have a rare square planar coordination geometry.
Two different color silver(I) complexes were obtained
by using two different solvents. Also, the thermal
degradation behavior of these complexes is discussed
Scheme 1..
1. Introduction
The study of the self-assembling process of metal
complexes continues to be a theme of considerable
current interest in the context of developing new solid-
state polymeric materials with specific architectural and
functional features [1]. The silver(I) ions are regarded as
extremely soft acids favoring coordination to soft bases,
such as ligands containing S and unsaturated N. Sil-
ver(I) complexes with these soft ligands give rise to an
interesting array of stereochemistries and geometric
configurations, with the coordination numbers of two
to six all occurring. Therefore, silver(I) is often used to
construct network structures [2]. However, a silver(I)
coordination polymer having a square planar geometry
has never been reported. Silver complexes with macro-
* Corresponding author. Tel.: +81-6-6721 2332; fax: +81-6-6723
2721.
E-mail address: suenagay@chem.kindai.ac.jp (Y. Suenaga).
0020-1693/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(01)00719-8

106
Y. Suenaga et al. / Inorganica Chimica Acta 328 (2002) 105–110
2. Experimental
2.1. General
lated. Yield: 43% based on silver. IR (KBr disc): w
(cm−1) 3022w, 2918m, 2868w, 1595m, 1491s, 1450m,
1
1278m, 1014m, 848s, 804s, 557s, 489s. H NMR (300
MHz, d8-THF): lH (ppm) 2.51 (18H, s), 6.82–6.85
(12H, d), 6.95–6.98 (12H, d). (Found: C, 54.32; H,
3.92; S, 18.00. Calc. for C48H42AgF6PS6: C, 54.18; H,
3.98; S, 18.08%).
Preparations were performed using the usual Schlenk
techniques. All solvents were dried and distilled by
standard methods before use. The standard chemicals
were obtained from Wako Chemical Co., Japan, and
used without further purification. The IR spectra were
measured as KBr discs on a JASCO FT-8000 spectrom-
eter. The 1H NMR spectra were obtained with a Varian
MERCURY-300 FT spectrometer at 23 °C. Te-
tramethylsilane was used as the internal reference.
Thermal analyses were performed on a SEIKO Instru-
ment Co. Ltd. TG/DTA 200 with a scanning rate of
10 °C min−1 when heating an atmosphere of nitrogen
(200 ml min−1). Diffuse reflection spectra were ob-
tained with a HITACHI U-4000 in the 350–800 nm
range.
2.2.3. [Ag(htsb)(2-butanone)](PF6) (2)
Crystals suitable for X-ray analysis were obtained by
procedures similar to complex 1. AgPF6 (2.53 mg, 2
mM) was dissolved in 5 cm3 of 2-butanone and to this
solution was added 2-butanone solution (5 cm3) con-
taining htsb (8.11 mg, 2 mM) and layered with 2 cm3 of
n-pentane as the diffusion solvent. After standing for 7
days at ambient temperature, orange plate crystals of
complex 2 were isolated. Yield: 36% based on silver. IR
(KBr disc): w (cm−1) 3026w, 2922m, 2866m, 1687m,
1491s, 1381m, 1278m, 1184m, 1076m, 1014m, 848s,
798s, 557s, 486s. 1H NMR (300 MHz, d8-THF): lH
(ppm) 2.55 (18H, s), 6.82–6.84 (12H, d), 6.95–6.97
(12H, d). (Found: C, 54.58; H, 4.39; S, 16.23. Calc. for
C52H50AgF6OPS6: C, 54.97; H, 4.44; S, 16.93%).
2.2. Syntheses
2.2.1. htsb
Ligand htsb was synthesized essentially according to
a literature [6] method. Recrystallization from CHCl3-
n-pentane yielded yellow needles (84%), m.p. 196–
198 °C. IR (KBr disc): w (cm−1) 3071w, 3020m, 2922s,
2855s, 1489s, 1450m, 1273m, 1176m, 1076m, 1016s,
810s, 491s, 416m. H NMR (300 MHz, d8-THF): lH
(ppm) 2.58 (18H, s), 6.80–6.83 (12H, d), 6.93–6.96
(12H, d). EI Mass spectrum: m/z 811 (100%, M).
2.3. Crystallography
The single crystal structure was solved by a direct
method and refined by a full-matrix least-square analy-
sis on F2. Data collection for these complexes was
performed on a Quantum CCD area detector coupled
with a Rigaku AFC-7R diffractometer. All the full-oc-
cupancy non-hydrogen atoms were anisotropically
refined. The positions of all the hydrogen atoms were
determined from the difference electron density maps
and included, but not refined. Atomic scattering factors
and anomalous dispersion terms were taken from the
usual sources. Computations were carried out using
TEXSAN [7].
1
2.2.2. [Ag(htsb)](PF6) (1)
Crystals suitable for X-ray analysis were obtained by
the reaction of AgPF6 (3.79 mg, 3 mM) dissolved in 5
cm3 of C3H6O and C3H6O solution (5 cm3) containing
htsb (3.04 mg, 0.75 mM). The mixture was stirred for 1
h and the yellow filtrate was transferred to a glass tube
and layered with 2 cm3 of n-pentane as the diffusion
solvent. After standing for 7 days at ambient tempera-
ture, yellow columnar crystals of complex 1 were iso-
2.3.1. Crystal data for [Ag(htsb)](PF6) (1)
C48H42AgF6PS6, M=1064.05, crystal dimensions
0.30×0.20×0.20 mm, monoclinic, space group P21/n
,
(no. 14), a=20.899(4), b=8.958(2), c=24.523(2) A,
3
,
i=99.139(1)°, V=4532(1) A , Z=4, Dcalc=1.559 g
cm−3, F(000)=2168.00, m(Mo Ka)=8.15 cm−1. T=
123 K, 10 314 reflections collected (Quantum CCD
diffractometer), 9686 unique reflections, 9681 [I\
2|(I)] were used in the final refinement, which con-
verged to R=0.054, Rw=0.096, with maximum
−3
,
residual electron density of 0.83 e A
.
2.3.2. Crystal data for [Ag(htsb)(2-butanone)](PF6) (2)
C52H50AgF6OPS6, M=1136.16, crystal dimensions
0.20×0.20×0.20 mm, monoclinic, space group P21/c
,
(no. 14), a=14.643(3), b=19.522(5), c=18.822(3) A,
3
,
Scheme 1.
i=94.48(1)°, V=5364(1) A , Z=4, Dcalc=1.407 g

Y. Suenaga et al. / Inorganica Chimica Acta 328 (2002) 105–110
107
Table 1
[6]. The range of the sulfur angles (99–102°) is smaller
than that (102–107°) found in the solid structure of the
[Ag(hphb)(NO3)]. As is well-known, silver(I) generally
adopts linear, trigonal, tetrahedral, and octahedral co-
ordination geometries. The square planar coordination
of silver(I) like these complexes were only described in
[Ag(cnpy)2](BF4) 8a (cnpy=4-cyanopyridine) and
[Ag(C10H7)]n [8b] (C10H7=1,1,2,4,5,5-hexacyano-3-aza-
penta-1,4-dienide), [AgL](ClO4)2 [8c] (L=1,4,8,11-
tetra-azacyclotetradecane), [Ag2(L)2]n [8d] (L=1,3-
bis(dicyanomethylidene)-indan). However, the silver ion
is surrounded by the four nitrogen atoms in all cases.
Crystallographic data for complexes 1 and 2
1
2
Empirical formula
Formula weight
T (K)
Crystal system
Space group
C48H42AgF6PS6
1064.05
123.0
monoclinic
P21/n (no. 14)
C
52H50AgF6OPS6
1136.16
300.0
monoclinic
P21/c (no. 14)
Unit cell dimensions
,
a (A)
20.899(4)
8.958(2)
24.523(2)
99.139(1)
14.643(3)
19.522(5)
18.822(3)
94.48(1)
,
b (A)
,
c (A)
i (°)
Unit cell volume
3
,
V (A )
Z
4532(1)
4
8.15
10 314
9681
5364(1)
4
6.95
13 171
4417
m(Mo Ka) (cm−1
Reflections measured
Observed reflections
)
[I\2|(I)]
R1
wR2
0.054
0.096
0.049
0.158
R1=ꢀ ꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀ ꢁFoꢁ, wR2=[ꢀ w(Fo2−Fc2)2/ꢀ w(Fo2)2]1/2
.
cm−3, F(000)=2328.00, m(Mo Ka)=6.95 cm−1. T=
296 K, 13 171 reflections collected 12314 unique
reflections, 4417 [I\2|(I)] were used in the final
refinement, which converged to R=0.049, Rw=0.158,
−3
,
with maximum residual electron density of 0.60 e A
(Table 1).
3. Results and discussion
AgPF6 dissolved in acetone is reacted at ambient
temperature with an acetone htsb solution, yellow sin-
gle crystals of complex 1 are observed. Upon perform-
ing the same reaction using 2-butanone, orange single
crystals of complex 2 are obtained. The infrared spectra
of 2 exhibit bands that can be readily assigned to the
carbonyl group from 2-butanone at 1687 cm−1. There-
fore, 2-butanone molecules link to metal ions in 2.
The molecular structure together with the atomic
numbering scheme is given in Fig. 1(a). A single-crystal
structure determination reveals that coordination com-
pound 1 contains an infinite zigzag chain structure. In
the cation, all htsb units are attached to the two silver
centers on the S atoms except for the para-position S
atoms. The AgꢀS distances are in the range of 2.5999–
,
2.6813 A. Each silver ion is coordinated by two htsb
donors in a square planar coordination sphere (Fig. 2).
The ligand acts as a bridge between pairs of Ag atoms
to produce a zigzag chain polymer. Six tolyl groups are
perpendicular to the core benzene ring plane in complex
1, with regular alternating, ababab as shown in [Ag(h-
phb)(NO3)] (hphb=hexakis(phenylsulfanyl)ꢀbenzene)
Fig. 1. (a) Zigzag chain structure of complex 1 (H atoms omitted for
,
clarity). Selected inter-atomic distances (A): Ag(1)ꢀS(1), 2.6813(6);
Ag(1)ꢀS(2), 2.5999(6); Ag(1)ꢀS(4), 2.6618(6); Ag(1)ꢀS(5), 2.6203(6).
Bond angles (°): S(1)ꢀAg(1)ꢀS(2), 75.88(2); S(1)ꢀAg(1)ꢀS(4),
178.58(2); S(1)ꢀAg(1)ꢀS(5), 104.94(2); S(2)ꢀAg(1)ꢀS(4), 102.74(2);
S(2)ꢀAg(1)ꢀS(5), 177.54(2); S(4)ꢀAg(1)ꢀS(5), 76.43(2). (b) Side view.
(c) Schematic view.

108
Y. Suenaga et al. / Inorganica Chimica Acta 328 (2002) 105–110
complexes 1 (yellow) and 2 (orange) have umax values of
480.2 and 536.6 nm, respectively. This difference of
color may be effect of a crystal packing of these
complexes.
The thermal degradation behaviors are shown in Fig.
5. In complex 1, a three-step decomposition is observed.
The drastic weight loss is 25.6% near 211 °C. Based on
the mass spectrometer measurement at the same time,
fragmentation ions corresponding to the tolyl sulfide
anions and the disulfide compounds were detected near
this temperature. This corresponds to two molecules of
tolyl sulfide anions (calculated 23.16%). In complex 2,
the elimination of 2-butanone coordinated in silver(I)
Fig. 2. Square planar coordination of silver(I) in complex 1, showing
50% thermal ellipsoids.
The silver(I) reported here is linked by four sulfur
atoms (htsb) giving the S(1)ꢀAgꢀS(4) angle of
178.58(2)°, S(2)ꢀAgꢀS(5) angle of 177.54(2)°, with the
sum of four angle SꢀAgꢀS being 359.99°. Also, the
silver(I) is weakly linked by the two sulfur atoms of
S(1) and S(4) rather than the other sulfur atoms. Thus,
this case represents a distorted square planar coordina-
tion geometry for silver(I). The ESR spectrum for the
crystal sample was measured at room temperature
which shows no signal, indicative of the same oxidation
state silver(I). Therefore, this special coordination ge-
ometry might be due to steric effects by the side tolyl
groups of htsb.
On the other hand, [Ag(htsb)(2-butanone)](PF6) (2)
were obtained by using 2-butanone in place of acetone
as the solvent. Similar to complex 1, the ligand acts as
a bridge between pairs of Ag atoms to produce a chain
polymer. However, the silver(I) coordination geometry
is different from complex 1. In complex 2, each silver
ion is coordinated by sulfur atoms of htsb donors and
one oxygen atom from the 2-butanone. As a result
silver ion has distorted pyramidal pentahedron geome-
try. The four AgꢀS distances are in the range of 2.631–
,
,
2.717 A. The Ag(1)ꢀO(1) distance is 2.330 A. The large
volume of complex 2 is due to high temperature of the
data collection and disorder. The crystal structure of
complex 2 were shown in Fig. 3(a) and (b). In contrast
zigzag chain structure of complexes 1 and 2 consist of a
linear chain structure (Table 2).
Fig. 3. (a) Linear chain structure of complex 2 (H atoms omitted for
,
clarity). Selected inter-atomic distances (A): Ag(1)ꢀS(1), 2.635(1);
Ag(1)ꢀS(2), 2.717(1); Ag(1)ꢀS(4), 2.678(1); Ag(1)ꢀS(5), 2.631(1);
Ag(1)ꢀO(1), 2.330(5). Bond angles (°): S(1)ꢀAg(1)ꢀS(2), 75.76(4);
S(1)ꢀAg(1)ꢀS(4), 94.35(4); S(1)ꢀAg(1)ꢀS(5), 155.96(5); S(2)ꢀAg(1)ꢀ
S(4), 145.44(5); S(2)ꢀAg(1)ꢀS(5), 99.40(4); S(4)ꢀAg(1)ꢀS(5), 76.18(4);
S(1)ꢀAg(1)ꢀO(1), 98.4(1); S(2)ꢀAg(1)ꢀO(1), 82.3(1); S(4)ꢀAg(1)ꢀO(1),
132.2(1); S(5)ꢀAg(1)ꢀO(1), 104.3(1). (b) Side view. (c) Schematic view.
As shown in Fig. 4, the powder reflectance spectra of
these complexes are clearly different. The spectra of

Y. Suenaga et al. / Inorganica Chimica Acta 328 (2002) 105–110
109
Table 2
Selected bond lengths (A) and angles (°) for complexes 1 and 2
In conclusion, the htsb ligand reacts with silver(I) to
form a 1:1 metal–ligand complex. The two para-posi-
tion S atoms in the htsb ligand are not coordinated to
the silver atom to consist of a zigzag chain, thus the
silver(I) ion has a rare square planar geometry. The
thermal degradation occurs in a three-step pattern. In
complex 1, the elimination of two tolyl sulfides occurs
near 211 °C. This may be the result from the silver(I)
ion having a rare square planar geometry in complex 1.
,
1
2
Bond lengths
Ag(1)ꢀS(1)
Ag(1)ꢀS(2)
Ag(1)ꢀS(4)
Ag(1)ꢀS(5)
2.6813(6)
2.5999(6)
2.6618(6)
2.6203(6)
Ag(1)ꢀS(1)
Ag(1)ꢀS(2)
Ag(1)ꢀS(4)
Ag(1)ꢀS(5)
Ag(1)ꢀO(1)
2.635(1)
2.717(1)
2.678(1)
2.631(1)
2.330(5)
Bond angles
S(1)ꢀAg(1)ꢀS(2)
75.88
S(1)ꢀAg(1)ꢀS(2)
S(1)ꢀAg(1)ꢀS(4)
S(1)ꢀAg(1)ꢀS(5)
S(1)ꢀAg(1)ꢀO(1)
S(2)ꢀAg(1)ꢀS(4)
S(2)ꢀAg(1)ꢀS(5)
S(2)ꢀAg(1)ꢀO(1)
S(4)ꢀAg(1)ꢀS(5)
S(4)ꢀAg(1)ꢀO(1)
S(5)ꢀAg(1)ꢀO(1)
75.76(4)
94.35(4)
155.96(5)
98.4(1)
145.44(5)
99.40(4)
82.3(1)
76.18(4)
132.2(1)
104.3(1)
S(1)ꢀAg(1)ꢀS(4) 178.58(2)
S(1)ꢀAg(1)ꢀS(5) 104.94(2)
S(2)ꢀAg(1)ꢀS(4) 102.74(2)
S(2)ꢀAg(1)ꢀS(5) 177.54(2)
4. Supplementary material
See http://www.rsc.org/suppdata/dt/2001/…/ for
crystallographic files in .cif format. Crystallographic
data for the structural analysis have been deposited
with the Cambridge Crystallographic Data Centre,
CCDC No. 170481 ([Ag(htsb)](PF6)) and 170482
([Ag(htsb)(2-butanone)](PF6)). Copies of this informa-
tion may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB21 EZ, UK
(fax: +44-1223-336-033; e-mail: deposit@ccdc.cam.
ac.uk or www: http://www.ccdc.cam.ac.uk).
S(4)ꢀAg(1)ꢀS(5)
76.43(2)
Acknowledgements
This work was supported by a Grant-in-Aid for
Scientific Research (c) (no. 12640547) from Japan Soci-
ety for the Promotion of Science and Kinki University
(no. RK13-6). The authors thank Dr. K. Sugimoto and
Mr. M. Anahata for his assistance with the X-ray
measurements. Also, the authors thank Professor S. Ito
and Dr. M. Iwasaki (Kinki University) for powder
reflectance spectra measurements.
Fig. 4. Powder reflectance spectra of: (a) complex 1; (b) complex 2.
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