research communications
2(μ-SCN)2(NH3)4
of AgaAnorganische Chemie, Fluorchemie, Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032 Marburg, Germany
*Correspondence e-mail: florian.kraus@chemie.uni-marburg.de
Di-μ-thiocyanato-bis[diamminesilver(I)], [Ag2(μ-SCN)2(NH3)4], was synthesized by the reaction of AgSCN with anhydrous liquid ammonia. In the binuclear molecule, the AgI atom is coordinated by two ammine ligands and the S atom of one thiocyanate ligand. Two of these [Ag(SCN)(NH3)2] units are bridged by the S atoms of the thiocyanate anions at longer distances, leading to a dimer with symmetry C2. The distance between the AgI atoms in the dimer is at 3.0927 (6) Å within the range of argentophilic interactions. The displays N—H⋯N and N—H⋯S hydrogen-bonding interactions that build up a three-dimensional network.
Keywords: crystal structure; silver thiocyanate; ammonia; argentophilicity.
CCDC reference: 1482850
1. Chemical context
The reactions of various silver salts with liquid ammonia and their products are in almost all cases still unknown. In textbooks, the formation of the linear diamminesilver(I) cation is often predicted without any structural evidence. In this contribution we want to report on the reaction and the product of AgSCN with liquid ammonia at 237 K. A dinuclear AgI complex was obtained.
2. Structural commentary
All atoms are located on general sites. The silver atom Ag1 is surrounded by two ammine ligands (N2 and N3) with distances of 2.269 (2) and 2.248 (2) Å, respectively. These values are in good agreement with other reported Ag—N distances (Zachwieja & Jacobs, 1989). The thiocyanate anion coordinates with its soft sulfur atom to the silver atom at a distance of 2.5363 (6) Å, which is similar compared to those of pure AgSCN (Lindqvist, 1957). The S—C—N angle in this pseudo-halide anion is with 178.2 (2)° almost linear. Two of the [Ag(SCN)(NH3)2] units are connected to each other via bridging S atoms of the thiocyanato ligands into a dimer located about a twofold rotation axis (Fig. 1). The resulting around Ag1 is that of a distorted tetrahedron where one short Ag—S distance [2.5363 (6) Å] and a long one [3.0533 (7) Å] are observed. Therefore, the bond towards the latter may be regarded as weaker. In the dimer, the two tetrahedra are connected through one edge into a double tetrahedron. It is interesting to note that the two SCN− anions point in the same direction as there is no center of inversion within the molecule but only the twofold rotation axis of the space-group type. The Ag⋯Ag distance is short at 3.0927 (6) Å, and is clearly in the range of argentophilic interactions (Jansen, 1987; Zachwieja & Jacobs, 1989; Schmidbaur & Schier, 2015).
3. Supramolecular features
The dinuclear complexes are connected to others via hydrogen bonds between the ammine ligands (N2 and N3) as donors and the N1 and S1 atoms of the thiocyanato ligand as acceptors. A three-dimensional network is formed in which each [Ag(SCN)(NH3)2] unit is coordinated by four (Fig. 2) and the dimer by eight other molecules. Six are arranged like a hexagon around the central molecule with all SCN ligands pointing in the same direction. Two molecules reside above and below this fictitious plane and are shifted towards a corner of the hexagon whereby the SCN ligands point in the opposite direction. Each of these two molecules shows the same coordination as described above, and overall, an AB-stacking of the molecules along [001], similar to the hexagonal closest packing, is obtained. The is shown in Fig. 3. It should be noted that no acceptor atom for the hydrogen atom H2A is present in the neighbourhood within the range of the sum of the van der Waals radii of H and N atoms. Numerical details of the hydrogen bonding are given in Table 1.
4. Synthesis and crystallization
400 mg (2.41 mmol) of AgSCN were placed in a flame-dried Schlenk tube under argon. Approximately 0.5 ml of liquid ammonia were condensed into the reaction vessel. The reaction vessel was stored at 237 K. After two weeks, colorless crystals of suitable size for X-ray diffraction were obtained from the colorless solution. The formation of the title compound is shown in the scheme.
5. Refinement
Crystal data, data collection and structure . All hydrogen atoms of the ammine ligands were located from a difference Fourier map and were refined isotropically without further restraints.
details are summarized in Table 2
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Supporting information
CCDC reference: 1482850
https://doi.org/10.1107/S2056989016008823/wm5294sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989016008823/wm5294Isup2.hkl
Data collection: X-AREA (Stoe & Cie, 2011); cell
X-AREA (Stoe & Cie, 2011); data reduction: X-RED32 (Stoe & Cie, 2009); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b) and SHELXLE (Hübschle et al., 2011); molecular graphics: DIAMOND (Brandenburg, 2015); software used to prepare material for publication: publCIF (Westrip, 2010).[Ag2(SCN)2(NH3)4] | F(000) = 768 |
Mr = 400.04 | Dx = 2.382 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
a = 12.8263 (9) Å | Cell parameters from 13119 reflections |
b = 7.1879 (3) Å | θ = 3.2–35.2° |
c = 12.2478 (9) Å | µ = 3.85 mm−1 |
β = 98.936 (6)° | T = 100 K |
V = 1115.47 (12) Å3 | Block, colorless |
Z = 4 | 0.26 × 0.16 × 0.14 mm |
Stoe IPDS 2T diffractometer | 1690 independent reflections |
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus | 1593 reflections with I > 2σ(I) |
Plane graphite monochromator | Rint = 0.028 |
Detector resolution: 6.67 pixels mm-1 | θmax = 30.5°, θmin = 3.2° |
rotation method scans | h = −18→18 |
Absorption correction: numerical (X-RED32 and X-SHAPE; Stoe & Cie, 2009) | k = −10→9 |
Tmin = 0.768, Tmax = 0.918 | l = −17→17 |
7257 measured reflections |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.029 | All H-atom parameters refined |
wR(F2) = 0.061 | w = 1/[σ2(Fo2) + (0.0131P)2 + 6.0057P] where P = (Fo2 + 2Fc2)/3 |
S = 1.11 | (Δ/σ)max < 0.001 |
1690 reflections | Δρmax = 1.26 e Å−3 |
79 parameters | Δρmin = −1.82 e Å−3 |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
Ag1 | 0.06012 (2) | 0.01303 (3) | 0.14990 (3) | 0.04102 (10) | |
S1 | −0.13234 (4) | 0.10809 (8) | 0.10715 (5) | 0.01844 (11) | |
N1 | −0.11243 (17) | 0.4982 (3) | 0.10139 (18) | 0.0226 (4) | |
N2 | 0.17384 (18) | 0.2371 (3) | 0.11205 (19) | 0.0217 (4) | |
N3 | 0.10144 (16) | −0.2907 (3) | 0.16630 (18) | 0.0189 (4) | |
C1 | −0.11906 (16) | 0.3371 (3) | 0.10457 (17) | 0.0162 (4) | |
H2A | 0.187 (3) | 0.315 (6) | 0.169 (3) | 0.037 (10)* | |
H2B | 0.228 (3) | 0.181 (7) | 0.101 (4) | 0.050 (12)* | |
H2C | 0.150 (3) | 0.311 (5) | 0.055 (3) | 0.034 (9)* | |
H3A | 0.158 (3) | −0.322 (5) | 0.140 (3) | 0.029 (9)* | |
H3B | 0.110 (3) | −0.331 (5) | 0.231 (3) | 0.033 (9)* | |
H3C | 0.050 (3) | −0.355 (6) | 0.125 (3) | 0.039 (10)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Ag1 | 0.02898 (12) | 0.02005 (11) | 0.0765 (2) | 0.00256 (8) | 0.01589 (11) | 0.01630 (11) |
S1 | 0.0185 (2) | 0.0165 (2) | 0.0201 (2) | −0.00265 (19) | 0.00216 (18) | 0.00010 (19) |
N1 | 0.0216 (9) | 0.0201 (10) | 0.0247 (10) | 0.0003 (7) | −0.0008 (7) | −0.0002 (8) |
N2 | 0.0245 (10) | 0.0190 (9) | 0.0220 (10) | 0.0006 (8) | 0.0048 (8) | 0.0022 (8) |
N3 | 0.0177 (9) | 0.0204 (9) | 0.0191 (9) | 0.0000 (7) | 0.0045 (7) | 0.0008 (7) |
C1 | 0.0139 (9) | 0.0217 (10) | 0.0126 (8) | 0.0000 (7) | 0.0009 (7) | −0.0011 (8) |
Ag1—N3 | 2.248 (2) | N2—H2A | 0.89 (4) |
Ag1—N2 | 2.269 (2) | N2—H2B | 0.83 (5) |
Ag1—S1 | 2.5363 (6) | N2—H2C | 0.89 (4) |
Ag1—S1i | 3.0533 (7) | N3—H3A | 0.87 (4) |
Ag1—Ag1i | 3.0927 (6) | N3—H3B | 0.83 (4) |
S1—C1 | 1.656 (2) | N3—H3C | 0.90 (4) |
N1—C1 | 1.162 (3) | ||
N3—Ag1—N2 | 123.89 (8) | Ag1—N2—H2C | 115 (2) |
N3—Ag1—S1 | 119.24 (6) | H2A—N2—H2C | 104 (3) |
N2—Ag1—S1 | 113.74 (6) | H2B—N2—H2C | 111 (4) |
N3—Ag1—Ag1i | 93.95 (5) | Ag1—N3—H3A | 115 (2) |
N2—Ag1—Ag1i | 125.28 (6) | Ag1—N3—H3B | 115 (3) |
S1—Ag1—Ag1i | 64.820 (16) | H3A—N3—H3B | 105 (3) |
C1—S1—Ag1 | 99.91 (8) | Ag1—N3—H3C | 108 (3) |
Ag1—N2—H2A | 109 (3) | H3A—N3—H3C | 104 (3) |
Ag1—N2—H2B | 105 (3) | H3B—N3—H3C | 109 (3) |
H2A—N2—H2B | 113 (4) | N1—C1—S1 | 178.2 (2) |
Symmetry code: (i) −x, y, −z+1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H2C···N1ii | 0.89 (4) | 2.34 (4) | 3.230 (3) | 171 (3) |
N2—H2B···N1iii | 0.83 (5) | 2.43 (5) | 3.255 (3) | 170 (4) |
N3—H3C···N1iv | 0.90 (4) | 2.31 (4) | 3.128 (3) | 151 (3) |
N3—H3B···N1v | 0.83 (4) | 2.39 (4) | 3.208 (3) | 168 (4) |
N3—H3A···S1iii | 0.87 (4) | 2.82 (4) | 3.672 (2) | 166 (3) |
Symmetry codes: (ii) −x, −y+1, −z; (iii) x+1/2, y−1/2, z; (iv) x, y−1, z; (v) −x, y−1, −z+1/2. |
Acknowledgements
The authors would like to thank Hendrik Borkowski for his preparative work. FK thanks the Deutsche Forschungsgemeinschaft for his Heisenberg professorship.
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