Synthesis and crystal structure of a silver(I) complex with dithioether ligand

Article abstract of DOI:10.1007/s10870-005-9049-1

The reaction of the dithioether ligand, 2,3-bis(5-methyl-1,3,4-thiadiazole- 2-thiomethyl) quinoxaline (L) with AgBF₄, leads to the formation of a novel complex {[AgL](BF₄)}_∞ 1, which has been characterized by single-crystal X-ray diffraction analysis: monoclinic, space group C2/c, with a = 20.316(7) A, b = 12.401(4) A, c = 18.039(6) A, β = 108.404(6)° and V = 4312(3) A³. The crystal structure of the complex consists of 1D {[AgL]⁺} _∞ cation chain and BF₄ ^- anions. In 1, the coordination geometry of Ag^I center can be best described as trigonal planar coordinated by three N from two distinct L ligands. The ligand is polydentate with one end adopting a bidentate conformation to chelate an Ag^I atom and the other end monodentate to bridge another Ag ^I resulting in an infinite chain along b axis. There exist Ag...N weak coordination, π-π stacking and F...S weak interactions in the complex, and these weak interactions link the 1D complex into 3D supramolecular structure and further stabilize the crystal structure in the solid state.

Full text of DOI:10.1007/s10870-005-9049-1

Journal of Chemical Crystallography, Vol. 36, No. 3, March 2006 (ꢀC 2006)
DOI: 10.1007/s10870-005-9049-1
Synthesis and crystal structure of a silver(I) complex with
dithioether ligand
(1)∗
(2)
(2)
Ya-Bo Xie,
Jian-Rong Li, and Xian-He Bu
Received June 8, 2005; accepted October 12, 2005
Published Online January 24, 2006
The reaction of the dithioether ligand, 2,3-bis(5-methyl-1,3,4-thiadiazole-2-thiomethyl)
quinoxaline (L) with AgBF4, leads to the formation of a novel complex {[AgL](BF4)}∞ 1,
which has been characterized by single-crystal X-ray diffraction analysis: monoclinic, space
◦
group C2/c, with a = 20.316(7) A˚ , b = 12.401(4) A˚ , c = 18.039(6) A˚ , β = 108.404(6)
3
+
and V = 4312(3) A˚ . The crystal structure of the complex consists of 1D {[AgL] }∞
−
I
cation chain and BF4 anions. In 1, the coordination geometry of Ag center can be
best described as trigonal planar coordinated by three N from two distinct L ligands.
The ligand is polydentate with one end adopting a bidentate conformation to chelate an
I
I
Ag atom and the other end monodentate to bridge another Ag resulting in an infinite
chain along b axis. There exist Ag· · ·N weak coordination, π–π stacking and F· · ·S
weak interactions in the complex, and these weak interactions link the 1D complex
into 3D supramolecular structure and further stabilize the crystal structure in the solid
state.
KEY WORDS: Crystal structure; dithioether ligand; silver(I) complex; weak interactions.
Introduction
such ligands offer the possibility for the con-
struction of unprecedented frameworks with tai-
8
The suitable organic ligands favoring
lored properties and functions. In our previous
work, the rationally designed dithioether lig-
ands with flexible spacers have been success-
fully used to construct various structures of com-
plexes including discrete molecules, 1D, 2D,
structure-specific self-assembly are the basis
for the construction of coordination architec-
1
–5
tures.
Recently, increasing attention has been
paid to the use of flexible bridging units in
the construction of supramolecular architec-
9
–12
and 3D network architectures.
As a con-
6,7
tures, and this approach is attractive because
the flexibility and conformation freedoms of
tinuation of our series of research on silver(I)
coordination compounds with dithioether lig-
ands, a multi-dentate dithioether ligand contain-
ing a aromatic spacers, 2,3-bis(5-methyl-1,3,4-
(
1)
2)
thiadiazole-2-thiomethyl)quinoxaline (L), and a
Collage of Environmental and Energy Engineering, Beijing Uni-
versity of Technology, Beijing 100022, China.
Department of Chemistry, Nankai University, Tianjin 300071,
China.
To whom correspondence should be addressed; e-mail:
xieyabo@bjut.edu.cn
I
new Ag complex of this ligand, {[AgL](BF )}
4
∞
(
1
, have been synthesized and characterized. We
I
∗
report herein the construction of the novel Ag
coordination polymer.
2
11
1
074-1542/06/0300-0211/0 ꢀC 2006 Springer Science+Business Media, Inc.

2
12
Xie, Li, and Bu
with the appropriate 5-methyl-2-sulfanyl-1,3,4-
thiadiazole, in the presence of KOH, gaves
the ligand 2,3-bis(5-methyl-1,3,4-thiadiazole-2-
thiomethyl)quinoxaline (L) in good yields (84%),
1
and the product was characterized by H NMR
and elemental analyses. Anal. Found: C, 45.74; H,
3
.49; N, 20.28. Calcd. for C H N S : C, 45.91;
16 14 6 4
1
H, 3.37; N, 20.08. H NMR (CDCl ): δ 2.72 (s,
3
6
H, –CH ), 5.10 (s, 4H, –SCH –), 7.73 ∼ 8.07
3
2
Experimental
(
m, 4H, Ar–H).
Materials and general methods
Synthesis of the silver(I) complex
[AgL](BF )} (1)
All reagents for synthesis and analyses were
of analytical grade and used as received. Ele-
mental analyses were performed on a Perkin-
Elmer 240C analyzer. IR spectra (KBr pellets)
were taken on an FT-IR 170SX (Nicolet) spec-
{
4
∞
The solution of AgBF4 (0.1 mmol) in
CH CN (3 mL) was slowly added to the solution
3
of L (0.1 mmol) in CHCl (3 mL). Slow diffu-
3
1
trometer. H NMR spectra were measured on
sion of ether into the resulted solution yielded
yellow single crystals of 1 suitable for X-ray
analysis with a yield of 32%. IR (KBr, cm ):
a Bruker AC-P500 spectrometer (300 MHz)
◦
at 25 C with tetramethylsilane as the internal
–1
reference.
1
1
698 w, 1633 w, 1569 w, 1489 m, 1427 w, 1402 m,
210 m, 1063 vs, 777 m, 521 w; analysis calcu-
lated for C H AgBF N S : C, 31.34; H, 2.30;
N, 13.70%; found: C, 31.68; H, 2.43; N, 13.51%.
16
14
4
6 4
Synthesis of the ligand 2,3-bis(5-methyl-1,3,4-
thiadiazole-2-thiomethyl)quinoxaline (L)
The ligand L was prepared according to
Scheme 1. 1,4-dibromo-2,3-butanedione was syn-
thesized by the adoption of a literature pro-
cedure. 2,3-bis(bromomethyl)quinoxaline was
prepared by the condensation reaction of
an equimolar amount of 1,4-dibromo-2,3-
butanedione and 1,2-diaminobenzene in ethanol
at reflux for ca. 2 h with a yield of 83%.
The reaction of 2,3-bis(bromomethyl)quinoxaline
X-ray crystallographic study of the complex 1
Single crystal X-ray diffraction was car-
ried out on a Bruker Smart 1000 diffractome-
ter. Intensities of reflections were measured us-
ing graphite monochromatized Mo-Ka radiation
13
˚
(λ = 0.71073 A) with ω-ϕ scan mode at 293(2) K
◦
in the range of 2.11 <
θ
< 26.38 . Unit
cell dimensions were obtained with least-squares
Scheme 1

Synthesis and crystal structure of a silver(I) complex
213
refinements and semi-empirical absorption cor-
Table 2. Selected Bond Lengths (
A˚ ) and
◦
Angles ( ) for Complex 1
14
rections were applied using SADABS program.
15
The structure was solved by direct method. The
silver(I) atoms were located from E-maps and
the other non-hydrogen atoms were obtained in
successive difference Fourier syntheses. The final
refinement was performed by full-matrix least-
Ag(1)–N(6)#
Ag(1)–N(3)
Ag(1)–N(1)
2.217(3)
2.376(3)
2.311(3)
2.933
Ag· · ·F (weak)
Ag· · ·N (weak)
2.648
#–
N(6) Ag(1) N(1)
–
148.01(10)
99.47(10)
108.42(10)
2
N(1)
–
Ag(1)–N(3)
squares methods on F by SHELXL-97 program
#
16
N(6) –Ag(1)–N(3)
package. Hydrogen atoms were included in cal-
culated positions and refined with fixed thermal
parameters riding on the parent atoms. Crystallo-
graphic data and experimental details for struc-
tural analysis are summarized in Table 1. And
selected bond lengths and angles are presented in
Table 2. CCDC-274527 contains the supplemen-
tary crystallographic data for complex 1. The data
can be obtained from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; Fax: +44-1223-336033; E-mail:
deposit@ccdc.cam.ac.uk.
Symmetry code: x, y−1, z.
Results and discussion
The flexible dithioether ligand L contains
rich structural information in which both the six
nitrogen atoms and the four sulfur atoms can act
as potential donors to coordinate to metal ions,
and the flexible nature of the ligand allows the
ligand to bend and rotate when coordinating to
metal centers so as to conform to the coordination
geometries of metal ions. Multifunctional organic
ligands with several potential coordination sites
have the ability to interact with their surround-
ings in addition to their usual function of bind-
ing to the transition metal, for instance through
weak coordinations or weak interactions, forming
supramolecular aggregates. Due to the flexibility
and conformational freedom of the ligand L, it is
a suitable candidate for investigating the roles of
supramolecular interactions and other factors that
control the network topologies in the aggregation
Table 1. Crystal Data and Structure Refinement Summary for
Complex 1
Empirical formula
Formula weight
Temperature (K)
Wavelength ( A˚ )
C16H14AgBF4N6S4
613.25
293(2)
0.71073
Crystal system
Space group
Unit cell dimensions
a ( A˚ )
monoclinic
C2/c
20.316(7)
b ( A˚ )
12.401(4)
I
c ( A˚ )
β ( )
Volume ( A˚ )
18.039(6)
108.404(6)
4312(3)
of coordination architectures. Ag as a soft acid,
◦
being inclined to coordinate to soft bases such
as S- and unsaturated N-containing ligands, is a
favorable and fashionable building block or con-
necting node for coordination polymers. In our
experiment, we attempt to investigate some coor-
dination features of the ligand by the reaction of
the dithioether ligand L with AgBF4.
3
Z
8
3
Dcalcd (g/cm )
1.889
1.375
2432
–
1
µ (mm
F (0 0 0)
Crystal size (mm )
θ range for data collection ( )
Range of h, k, l
)
3
0.40 × 0.24 × 0.20
o
2.11/26.38
–25/15, –15/14, –20/22
9849/4275 [Rint = 0.0250]
1.0000 and 0.7691
4275/0/290
Reflections collected/unique
Max. and min. transmission
The resulting complex 1 consists of 1D
+
+
−
{
[AgL] } cation chain and BF anions. In
∞
∞
4
I
Data/restraints/parameters
Goodness-of-fit on F2
{[AgL] }
cation chain, each Ag center is co-
1.022
Final R indices [I > 2σ(I)]
R indices (all data)
Largest diff. peak and hole (e/ A˚ )
R1 = 0.0352, wR2 = 0.0766
R1 = 0.0532, wR2 = 0.0832
0.745 and –0.605
ordinated by three N atoms from two distinct L
ligands (Fig. 1), and the coordination geometry
of Ag center can be best described as trigonal
3
I

2
14
Xie, Li, and Bu
Fig. 1. ORTEP view with atom labeling (displacement ellipsoids drawn at 30% probability)
of the structure of complex 1.
Ag atoms with none S atoms coordinating to AgI
I
planar. Three Ag–N bond lengths of 99.47(10),
˚
108.42(10) and 148.01(10) A are unequal but
atom, indicating the coordination ability of N to
I
fall in the expected ranges for such coordination
Ag atom is stronger than that of S atom. In the
1
7
−
I
bonds. (Table 2). In addition, the BF anions
chain, the distance of adjacent Ag atoms is ca.
12.401 A. All quinoxaline rings in the chain are
almost in same plane.
4
I
˚
form weak coordination bonds to Ag centers with
˚
the Ag· · ·F distance of 2.933 A.
In 1, each ligand uses two N atoms (one from
An interesting feature of this complex is the
formation of Ag· · ·N weak interactions between
the terminal thiadiazole ring and another from
I
˚
quinoxaline ring) to chelate a Ag atom forming a
adjacent chains. The Ag· · ·N distance of 2.648 A
seven-member ring with chair conformation and
an N atom from another terminal thiadiazole ring
is significantly shorter than the sum of van der
18
˚
Waals radii of Ag and N (3.27 A), indicating
the existence of Ag· · ·N weak interactions, and
a double-strand chain structure is formed by this
weak interactions (Fig. 2). In the double-strand
chain, the adjacent quinoxaline and thiadiazole
ring are aligned in an off-set fashion, being ap-
proximately parallel to each other (the dihedral
angle is 15.4 ) with the centroid-centroid sepa-
ration of ca. 3.464 A, indicating the presence of
face-to-face π–π stacking interactions. The fur-
ther investigation of the packing structure found
I
to bridge another Ag atom resulting in an infinite
chain along b axis. The terminal thiadiazole ring
providing a bridging N donor is almost in the same
plane with the quinoxaline ring, and another thia-
diazole ring giving a chelating N donor lies above
the quinoxaline plane and incline each other with a
◦
◦
dihedral angle of 64.2 . Due to the coordination of
˚
an N atom of the quinoxaline ring, the two quinox-
aline rings are twisted relative to each other. The
silver atom lies above the quinoxaline plane with
19
˚
˚
the upright distance of 0.9886 A. Only three N
that the distance of F· · ·S of 3.044 A is shorter
atoms of each ligand take part in coordinating to
than the summed van der Waals radii of two atoms
Fig. 2. The double-strand chain of 1 formed by the Ag· · ·N weak coordination.

Synthesis and crystal structure of a silver(I) complex
215
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1
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