Diamminesilver(I) bis-(2-amino-5-nitro-benzoato-2 O 1,O1′)silver(I): A two-dimensional supra-molecular sheet with a short inter-sheet distance containing a rare four-coordinate planar silver(I) centre

Article abstract of DOI:10.1107/S0108270110020585

The asymmetric unit of the title compound, [Ag(NH₃) ₂][Ag(C₇H₅N₂O₄) ₂], comprises half an [Ag(NH₃)₂]⁺ cation and half an [Ag(anbz)₂]^- anion (anbz is 2-amino-5-nitro-benzoate). Both Ag^I ions are located on inversion centres. The cation has a linear coordination geometry with two symmetry-related ammine ligands. The Ag^I cation in the anionic part shows a rare four-coordinate planar geometry completed by two chelating symmetry-related anbz ligands. Intra- and inter-molecular N - H...O hydrogen bonds create a slightly undulating two-dimensional supra-molecular sheet. Adjacent sheets are only ca 3.3 A apart. Ag...O, Ag...N and π-π stacking inter-actions consolidate the packing of the mol-ecules in the solid state.

Full text of DOI:10.1107/S0108270110020585

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
cations (n = 1 or 2) (Zheng et al., 2007), which can be stabilized
by supramolecular interactions, only a limited number of
[Ag(NH3)2]-containing complexes have been documented,
due to the weak Ag—Nammine coordination bond (Zheng et al.,
2002; You et al., 2004; Pajunen & Pajunen 1994; Paul et al.,
2005; Zheng et al., 2008; Whitcomb & Rajeswaran 2008).
2-Amino-5-nitrobenzoate (H2anbz) is a multifunctional ligand
which can form not only the usual Ag—O coordination bonds
through its carboxyl group, but also Agꢁ ꢁ ꢁO and Agꢁ ꢁ ꢁN weak
interactions and hydrogen bonds using its amino and nitro
groups. However, the silver(I)–anbz complex has not been
reported until now. Recently, we reported some other silver(I)
complexes (Sun, Luo, Huang et al., 2009; Sun, Luo, Xu et al.,
2009; Sun, Luo et al., 2010; Sun, Zhang, Luo et al., 2010; Sun,
Zhang, Xu et al., 2010), and as an extension of our work on the
structural characterization of silver(I) complexes, the title
complex, (I), is reported here.
ISSN 0108-2701
Diamminesilver(I) bis(2-amino-5-
0
nitrobenzoato-j2O1,O1 )silver(I): a
two-dimensional supramolecular sheet
with a short intersheet distance
containing a rare four-coordinate
planar silver(I) centre
Di Sun,a Na Zhang,a Rong-Bin Huanga* and Lan-Sun
Zhengb
aDepartment of Chemistry, College of Chemistry and Chemical Engineering, Xiamen
University, Xiamen 361005, People’s Republic of China, and bState Key Laboratory
for Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen 361005,
People’s Republic of China
Correspondence e-mail: rbhuang@xmu.edu.cn
Received 6 May 2010
Accepted 31 May 2010
Online 5 June 2010
The asymmetric unit in the structure of complex (I)
comprises half an [Ag(NH3)2]+ cation and half an [Ag-
(anbz)2]ꢀ anion (Fig. 1). Each AgI ion is on a special position
associated with the crystallographic inversion centre. One AgI
The asymmetric unit of the title compound, [Ag(NH3)2]-
[Ag(C7H5N2O4)2], comprises half an [Ag(NH3)2]+ cation and
half an [Ag(anbz)2]ꢀ anion (anbz is 2-amino-5-nitrobenzoate).
Both AgI ions are located on inversion centres. The cation has
a linear coordination geometry with two symmetry-related
ammine ligands. The AgI cation in the anionic part shows a
rare four-coordinate planar geometry completed by two
chelating symmetry-related anbz ligands. Intra- and inter-
molecular N—Hꢁ ꢁ ꢁO hydrogen bonds create a slightly
undulating two-dimensional supramolecular sheet. Adjacent
˚
sheets are only ca 3.3 A apart. Agꢁ ꢁ ꢁO, Agꢁ ꢁ ꢁN and ꢀ–ꢀ
stacking interactions consolidate the packing of the molecules
in the solid state.
Comment
In coordination chemistry, silver in the +1 oxidation state is
found to adopt a wide variety of coordination geometries due
to the lack of stereochemical preference arising from a d10
closed-shell configuration (Blake, Brooks et al., 1999; Blake,
Champness et al., 1999; Blake et al., 1997; Batten & Robson
1998; Yaghi et al., 2003). Coordination numbers for AgI from 2
to 8 have been observed (without including Agꢁ ꢁ ꢁAg inter-
actions), often with distorted coordination geometries owing
to the inherent lack of CFSE (crystal field stabilization
energy). However, square-planar AgI stereochemistry is
generally acknowledged as rare (Young & Hanton, 2008); the
first structurally characterized square-planar AgI complex was
a flavin complex (Fritchie, 1972). On the other hand, although
AgI under ammoniacal conditions can form [Ag(NH3)2]+n
Figure 1
The structure of (I), showing the atom-numbering scheme and the
coordination environment around the two different AgI centres.
Displacement ellipsoids are drawn at the 50% probability level and H
atoms are shown as small spheres of arbitrary radii. [Symmetry codes: (i)
ꢀx + 2, ꢀy + 2, ꢀz; (ii) ꢀx + 2, ꢀy + 1, ꢀz + 2.]
m174 # 2010 International Union of Crystallography
doi:10.1107/S0108270110020585
Acta Cryst. (2010). C66, m174–m176

metal-organic compounds
Figure 3
A perspective view of the three-dimensional supramolecular framework
of (I), showing intersheet hydrogen bonds and Agꢁ ꢁ ꢁO, Agꢁ ꢁ ꢁN and ꢀ–ꢀ
interactions as dashed lines. (In the electronic version of the paper, these
dashed lines are green, blue, purple and red, respectively.)
[symmetry code: (v) x ꢀ 1, y, z]. The intersheet distance is ca
˚
3.3 A, which is comparable with those of graphite and Ag6-
(benzene-1,3,5-tricarboxylic acid)2(2-aminopyrazine)6 (Sun,
Luo, Xu et al. 2009), and is a result of the fact that there are no
axial ligands perpendicular to the two-dimensional sheets.
The shortest centroid–centroid distance between parallel
Figure 2
˚
benzene rings of the anbz ligands is 3.8523 (9) A, with a large
A perspective view of the two-dimensional supramolecular sheet of (I),
incorporating intra- and intermolecular N—Hꢁ ꢁ ꢁO hydrogen bonds
(dashed lines).
˚
slippage of 2.065 A, which suggests the existence of weak
offset face-to-face ꢀ–ꢀ stacking interactions. These combine
with the inter-sheet ammine–nitro N—Hꢁ ꢁ ꢁO [mean Nꢁ ꢁ ꢁO
˚
distance = 3.131 (2) A] hydrogen bonds and Agꢁ ꢁ ꢁOnitro and
ion (Ag1) adopts a linear coordination environment, coordi-
nated by two symmetry-related ammonia molecules to form
the [Ag(NH3)2]+ cation. The Ag1—N3 bond length is
Agꢁ ꢁ ꢁNamino interactions to stabilize the resultant three-
dimensional supramolecular framework (Fig. 3).
˚
2.1193 (16) A, which is comparable with the corresponding
values observed in another silver(I)–ammonia complex (You
& Zhu, 2004). The other AgI ion (Ag2) is located in a rare
four-coordination planar environment (only ꢂ2% of all
reported silver complexes possess this stereochemistry (Young
& Hanton, 2008), which is completed by two chelating inver-
sion-related anbz ligands. This geometry is not a perfect
square-planar arrangement, but is distorted due to the acute
bite angle [53.02 (4)ꢃ] and differing Ag—O bond lengths
(Table 1), both of which are imposed by the asymmetrically
chelated ring.
Experimental
All reagents and solvents were obtained commercially and used
without further purification. A mixture of Ag2O (116 mg, 0.5 mmol)
and H2anbz (182 mg, 1 mmol) was stirred in a methanol–H2O mixed
solvent (10 ml, 1:1 v/v). An aqueous NH3 solution (25%, 0.5 ml) was
then added dropwise to the mixture to give a clear solution under
ultrasonic treatment. The resulting solution was allowed to evaporate
slowly in the dark at room temperature for several days to give
colourless crystals of (I), which were washed with a small volume of
cold ethanol and diethyl ether (yield 61%, based on Ag2O). Analysis
calculated for C14H16Ag2N6O8: C 27.47, H 2.63, N 13.73%; found:
C 27.51, H 2.59, N 13.64%.
There are abundant weak interactions around Ag1 and
i
˚
Ag2. Ag1ꢁ ꢁ ꢁO2 and Ag1ꢁ ꢁ ꢁN1 [3.1195 (15) and 3.1885 (16) A,
respectively; symmetry code: (i) x + 1, y, z ꢀ 1] are slightly
Crystal data
shorter than the sums of the van der Waals radii of Ag and O
[Ag(NH3)2][Ag(C7H5N2O4)2]
Mr = 612.07
Triclinic, P1
ꢃ = 62.077 (8)ꢃ
3
˚
˚
(3.24 A) and Ag and N (3.27 A) (Bondi, 1964). The
Ag2ꢁ ꢁ ꢁO2ii interaction [symmetry code: (ii) ꢀx + 2, ꢀy + 1,
ꢀz + 1] is along the axial direction above and below the AgO4
plane. A possible reason for the four-coordinate planar
geometry may be the steric shielding of axial sites by the nitro
groups (Reger et al., 2004).
˚
V = 456.86 (6) A
Z = 1
˚
˚
a = 7.1361 (5) A
Mo Kꢁ radiation
ꢄ = 2.20 mmꢀ1
T = 173 K
0.10 ꢄ 0.10 ꢄ 0.08 mm
b = 7.4070 (6) A
˚
c = 9.9686 (6) A
ꢁ = 87.064 (6)ꢃ
ꢂ = 79.170 (6)ꢃ
The anionic and cationic parts of (I) interact with each other
to form a one-dimensional zigzag chain through weak
Agꢁ ꢁ ꢁOnitro interactions, alternating with interionic N3—
H3Bꢁ ꢁ ꢁO1 hydrogen bonds (Table 2) to give a C22(6) chain-like
motif (Bernstein et al., 1995). Additionally, intra-anion N1—
H1Cꢁ ꢁ ꢁO4 hydrogen bonds, showing an S(6) motif, consoli-
date the one-dimensional chains, which are further linked into
a slightly undulating two-dimensional supramolecular sheet
(Fig. 2) via intermolecular N1—H1Bꢁ ꢁ ꢁO3v hydrogen bonds
Data collection
Oxford Xcalibur diffractometer
with a Sapphire3 Gemini Ultra
detector
Absorption correction: multi-scan
[CrysAlis Pro (Oxford
Diffraction, 2009); empirical
(using intensity measurements)
absorption correction using
spherical harmonics, imple-
mented in SCALE3 ABSPACK
scaling algorithm]
Tmin = 0.810, Tmax = 0.843
3721 measured reflections
1800 independent reflections
1627 reflections with I > 2ꢅ(I)
Rint = 0.014
ꢅ
Acta Cryst. (2010). C66, m174–m176
Sun et al.
[Ag(NH3)2][Ag(C7H5N2O4)2] m175

metal-organic compounds
Table 1
Selected geometric parameters (A, ).
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: SF3131). Services for accessing these data are
described at the back of the journal.
ꢃ
˚
Ag1—N3
Ag1—O2
Ag1—N1i
2.1193 (16)
3.1195 (15)
3.1885 (16)
Ag2—O3
Ag2—O4
Ag2—O2ii
2.2367 (12)
2.6541 (13)
2.9287 (15)
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0.88
0.88
0.91
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2.03
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3.185 (2)
3.077 (2)
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149
159
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˚
Áꢆmax = 0.47 e A
ꢀ3
˚
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˚
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˚
˚
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ꢅ
m176 Sun et al. [Ag(NH3)2][Ag(C7H5N2O4)2]
Acta Cryst. (2010). C66, m174–m176