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The structure of K[Ag(SCN)2] forms a three-dimensional network consisting of seven-coordinated K atoms and four-coordinated Ag atoms connected together by bridging thio­cyanate groups.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536801009679/br6023sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536801009679/br6023Isup2.hkl
Contains datablock I

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](N-C) = 0.006 Å
  • R factor = 0.036
  • wR factor = 0.095
  • Data-to-parameter ratio = 25.6

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


Yellow Alert Alert Level C:
ABSTM_02 Alert C The ratio of expected to reported Tmax/Tmin(RR) is > 1.10 Tmin and Tmax reported: 0.560 0.650 Tmin and Tmax expected: 0.442 0.655 RR = 1.276 Please check that your absorption correction is appropriate.
0 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check

Comment top

There has been considerable investigation into thiocyanates. A valuable synthetic study was published about 100 years ago (Wells, 1902) and treated mostly double and triple thiocyanates. At that time, most studies were synthetic and analytical. Many crystal structure determinations relating to metal thiocyanates have been solved since. Silver forms simple thiocyanate AgSCN, which has two polymorphic forms, Pmnn and C2/c. There are also double silver thiocyanates, and triple thiocyanates such as Cs3Sr[Ag2(SCN)7] and Cs3Ba[Ag2(SCN)7]. These two triple thiocyanates have also interesting optical, electro-optic and electrostrictive properties (Bohaty & Fröhlich, 1992).

Although potassium silver thiocyanate, Ag K(SCN)2, has been known for 150 years, there is little data available in the literature. The unit cell has been published (Chateau et al., 1962). Potassium silver thiocyanate, Ag K(SCN)2, is not isostructural with AgNH4(SCN)2, unlike many potassium and ammonium compounds.

Potassium is seven-coordinated, with five N and two S atoms around the K atom. The coordination polyhedron is a distorted monocapped trigonal prism, as shown in Fig. 1. N1 is the capping atom which is at a distance of 2.986 (4) Å from K1.

Four S atoms surround the Ag atom in the form of a tetrahedron. The tetrahedron is slightly distorted: Ag—S distances vary between 2.579 (1) and 2.739 (1) Å. The six S—Ag—S angles vary between 95.29 (3) and 126.49 (4)°.

There are two different thiocyanate groups in the structure. The bond lengths and angles are normal and similar in both groups, but differ in coordination. In thiocyanate group one (S1/C1/N1), the S atom is connected to two Ag atoms and the N atom to three K atoms, whereas in thiocyanate group two (S2/C2/N2), the S atom is connected to two Ag atoms and two K atoms and the N atom to two K atoms.

The structure forms a three-dimensional network. It can be thought of as consisting of infinite AgS2 layers, so that the tetrahedra around the Ag atoms are approximately at planes xz with y = 0.0 and 0.5 (Fig. 2) and the potassium polyhedra approximately at planes xz with y = 0.25 and 0.75. Tetrahedra around the Ag atoms share one common edge and two common corners so that one tetrahedron is connected to three other tetrahedra. The monocapped trigonal prisms around the K atoms share four common edges and two common corners. These layers are held together by the thiocyanate groups (Fig. 3).

Experimental top

Potassium thiocyanate was obtained from Fluka Chemie AG and silver thiocyanate by the Aldrich Chemical Company Inc. Potassium silver thiocyanate was made by dissolving 1670 mg KSCN into 3.3 ml deionized water and then dissolving 1230 mg AgSCN into that solution at room temperature. After slow evaporation at room temperature, white crystals of Ag K(SCN)2 formed after two days. The crystal used for analysis was mounted on a glass fibre.

Computing details top

Data collection: CAD-4 Software (Enra-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: CAD-4 Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 2000).

Figures top
[Figure 1] Fig. 1. The coordination polyhedron around the K atom.
[Figure 2] Fig. 2. The AgS2 layer viewed along the y axis. The x axis is horizontal.
[Figure 3] Fig. 3. The partial structure along the a axis. The z axis is horizontal. Ellipsoids are presented at the 50% probability level.
(I) top
Crystal data top
AgK(SCN)2Dx = 2.666 Mg m3
Mr = 263.13Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, PbcaCell parameters from 25 reflections
a = 6.719 (1) Åθ = 14.6–25.4°
b = 18.024 (1) ŵ = 4.23 mm1
c = 10.826 (2) ÅT = 293 K
V = 1311.0 (3) Å3Prism, colourless
Z = 80.2 × 0.2 × 0.1 mm
F(000) = 992
Data collection top
Enraf Nonius CAD-4
diffractometer
1137 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.000
Graphite monochromatorθmax = 30.0°, θmin = 2.3°
ω/2θ scansh = 09
Absorption correction: ψ scan
(North et al., 1968)
k = 025
Tmin = 0.56, Tmax = 0.65l = 015
1897 measured reflections2 standard reflections every 60 min
1897 independent reflections intensity decay: none
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.036 w = 1/[σ2(Fo2) + (0.046P)2 + 0.2326P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.095(Δ/σ)max = 0.001
S = 1.00Δρmax = 0.98 e Å3
1897 reflectionsΔρmin = 0.64 e Å3
74 parametersExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.0148 (6)
Crystal data top
AgK(SCN)2V = 1311.0 (3) Å3
Mr = 263.13Z = 8
Orthorhombic, PbcaMo Kα radiation
a = 6.719 (1) ŵ = 4.23 mm1
b = 18.024 (1) ÅT = 293 K
c = 10.826 (2) Å0.2 × 0.2 × 0.1 mm
Data collection top
Enraf Nonius CAD-4
diffractometer
1137 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.000
Tmin = 0.56, Tmax = 0.652 standard reflections every 60 min
1897 measured reflections intensity decay: none
1897 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.03674 parameters
wR(F2) = 0.0950 restraints
S = 1.00Δρmax = 0.98 e Å3
1897 reflectionsΔρmin = 0.64 e Å3
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Ag10.17017 (6)0.50256 (2)0.37237 (4)0.04619 (16)
K10.35256 (14)0.26974 (6)0.37357 (9)0.0381 (2)
S10.54341 (18)0.53295 (7)0.34950 (10)0.0339 (3)
S20.01889 (16)0.39124 (6)0.48980 (9)0.0304 (2)
C10.5208 (7)0.6245 (3)0.3470 (4)0.0327 (10)
C20.1691 (7)0.3682 (2)0.3970 (4)0.0304 (9)
N10.5050 (7)0.6887 (2)0.3502 (4)0.0486 (11)
N20.3002 (6)0.3505 (3)0.3362 (4)0.0477 (11)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ag10.0487 (3)0.0437 (2)0.0462 (2)0.01424 (18)0.00546 (18)0.00078 (17)
K10.0318 (5)0.0402 (5)0.0423 (5)0.0018 (4)0.0006 (5)0.0033 (5)
S10.0335 (6)0.0353 (6)0.0328 (5)0.0006 (5)0.0002 (5)0.0067 (5)
S20.0307 (5)0.0301 (5)0.0303 (5)0.0007 (5)0.0013 (4)0.0009 (4)
C10.028 (2)0.041 (3)0.029 (2)0.0031 (18)0.0040 (19)0.0011 (17)
C20.032 (2)0.0234 (19)0.036 (2)0.0034 (17)0.0054 (19)0.0041 (16)
N10.042 (2)0.042 (2)0.062 (3)0.001 (2)0.006 (2)0.000 (2)
N20.034 (2)0.056 (3)0.053 (3)0.008 (2)0.0007 (19)0.016 (2)
Geometric parameters (Å, º) top
Ag1—S12.5788 (13)K1—K1viii4.3915 (13)
Ag1—S22.5836 (11)S1—C11.658 (5)
Ag1—S1i2.6068 (12)S1—Ag1v2.6068 (12)
Ag1—S2ii2.7393 (11)S2—C21.666 (4)
K1—N2iii2.779 (4)S2—Ag1ii2.7393 (11)
K1—N1iv2.823 (5)S2—K1ix3.4431 (15)
K1—N2v2.885 (4)C1—N11.162 (6)
K1—N1vi2.986 (4)C2—N21.145 (6)
K1—N1vii3.228 (4)C2—K1i3.429 (4)
K1—S23.3771 (15)C2—K1ix3.518 (4)
K1—C2v3.429 (4)N1—K1x2.823 (5)
K1—S2viii3.4431 (15)N1—K1xi2.986 (4)
K1—C2viii3.518 (4)N1—K1vii3.228 (4)
K1—K1i4.2947 (13)N2—K1xii2.779 (4)
K1—K1v4.2947 (13)N2—K1i2.885 (4)
S1—Ag1—S2126.49 (4)N2iii—K1—K1v41.63 (9)
S1—Ag1—S1i100.64 (3)N1iv—K1—K1v127.57 (10)
S2—Ag1—S1i119.21 (4)N2v—K1—K1v77.75 (9)
S1—Ag1—S2ii110.78 (4)N1vi—K1—K1v40.88 (9)
S2—Ag1—S2ii95.29 (3)N1vii—K1—K1v110.20 (8)
S1i—Ag1—S2ii101.75 (4)S2—K1—K1v138.71 (3)
N2iii—K1—N1iv166.46 (13)C2v—K1—K1v60.06 (8)
N2iii—K1—N2v85.41 (12)S2viii—K1—K1v90.79 (2)
N1iv—K1—N2v83.55 (12)C2viii—K1—K1v118.18 (7)
N2iii—K1—N1vi82.47 (12)K1i—K1—K1v102.93 (4)
N1iv—K1—N1vi86.95 (12)N2iii—K1—K1viii62.19 (10)
N2v—K1—N1vi73.88 (13)N1iv—K1—K1viii128.54 (10)
N2iii—K1—N1vii76.39 (12)N2v—K1—K1viii147.59 (9)
N1iv—K1—N1vii117.10 (11)N1vi—K1—K1viii100.44 (9)
N2v—K1—N1vii135.84 (13)N1vii—K1—K1viii39.95 (8)
N1vi—K1—N1vii140.36 (15)S2—K1—K1viii112.37 (4)
N2iii—K1—S2105.79 (10)C2v—K1—K1viii130.47 (8)
N1iv—K1—S278.70 (10)S2viii—K1—K1viii49.26 (3)
N2v—K1—S274.35 (10)C2viii—K1—K1viii58.47 (7)
N1vi—K1—S2146.32 (10)K1i—K1—K1viii170.65 (3)
N1vii—K1—S272.61 (8)K1v—K1—K1viii77.878 (1)
N2iii—K1—C2v68.90 (12)C1—S1—Ag197.11 (16)
N1iv—K1—C2v98.93 (11)C1—S1—Ag1v102.95 (15)
N2v—K1—C2v18.45 (10)Ag1—S1—Ag1v111.19 (4)
N1vi—K1—C2v64.77 (11)C2—S2—Ag1101.23 (15)
N1vii—K1—C2v133.15 (11)C2—S2—Ag1ii98.67 (15)
S2—K1—C2v87.39 (8)Ag1—S2—Ag1ii84.71 (3)
N2iii—K1—S2viii103.37 (11)C2—S2—K196.73 (14)
N1iv—K1—S2viii83.03 (9)Ag1—S2—K193.39 (3)
N2v—K1—S2viii151.45 (11)Ag1ii—S2—K1164.56 (4)
N1vi—K1—S2viii80.34 (9)C2—S2—K1ix78.65 (14)
N1vii—K1—S2viii72.63 (8)Ag1—S2—K1ix173.46 (5)
S2—K1—S2viii127.00 (3)Ag1ii—S2—K1ix101.79 (4)
C2v—K1—S2viii144.81 (8)K1—S2—K1ix80.16 (3)
N2iii—K1—C2viii120.51 (13)N1—C1—S1177.4 (4)
N1iv—K1—C2viii70.26 (11)N2—C2—S2177.6 (4)
N2v—K1—C2viii153.82 (11)N2—C2—K1i52.9 (3)
N1vi—K1—C2viii103.90 (11)S2—C2—K1i127.7 (2)
N1vii—K1—C2viii61.46 (10)N2—C2—K1ix103.9 (3)
S2—K1—C2viii99.66 (8)S2—C2—K1ix73.67 (15)
C2v—K1—C2viii165.37 (10)K1i—C2—K1ix103.62 (10)
S2viii—K1—C2viii27.67 (7)C1—N1—K1x126.5 (4)
N2iii—K1—K1i124.46 (11)C1—N1—K1xi115.7 (3)
N1iv—K1—K1i43.82 (9)K1x—N1—K1xi95.30 (13)
N2v—K1—K1i39.79 (9)C1—N1—K1vii103.4 (3)
N1vi—K1—K1i75.24 (9)K1x—N1—K1vii92.81 (12)
N1vii—K1—K1i144.00 (8)K1xi—N1—K1vii122.88 (15)
S2—K1—K1i73.31 (2)C2—N2—K1xii135.1 (4)
C2v—K1—K1i55.56 (8)C2—N2—K1i108.7 (3)
S2viii—K1—K1i121.44 (2)K1xii—N2—K1i98.58 (13)
C2viii—K1—K1i114.05 (7)
Symmetry codes: (i) x1/2, y, z+1/2; (ii) x, y+1, z+1; (iii) x+1, y, z; (iv) x+1/2, y1/2, z; (v) x+1/2, y, z+1/2; (vi) x+1, y1/2, z+1/2; (vii) x+1, y+1, z+1; (viii) x+1/2, y+1/2, z+1; (ix) x1/2, y+1/2, z+1; (x) x+1/2, y+1/2, z; (xi) x+1, y+1/2, z+1/2; (xii) x1, y, z.

Experimental details

Crystal data
Chemical formulaAgK(SCN)2
Mr263.13
Crystal system, space groupOrthorhombic, Pbca
Temperature (K)293
a, b, c (Å)6.719 (1), 18.024 (1), 10.826 (2)
V3)1311.0 (3)
Z8
Radiation typeMo Kα
µ (mm1)4.23
Crystal size (mm)0.2 × 0.2 × 0.1
Data collection
DiffractometerEnraf Nonius CAD-4
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.56, 0.65
No. of measured, independent and
observed [I > 2σ(I)] reflections
1897, 1897, 1137
Rint0.000
(sin θ/λ)max1)0.703
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.036, 0.095, 1.00
No. of reflections1897
No. of parameters74
Δρmax, Δρmin (e Å3)0.98, 0.64

Computer programs: CAD-4 Software (Enra-Nonius, 1989), CAD-4 Software, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), DIAMOND (Brandenburg, 2000).

Selected geometric parameters (Å, º) top
Ag1—S12.5788 (13)K1—N1vii3.228 (4)
Ag1—S22.5836 (11)K1—S23.3771 (15)
Ag1—S1i2.6068 (12)K1—S2viii3.4431 (15)
Ag1—S2ii2.7393 (11)S1—C11.658 (5)
K1—N2iii2.779 (4)S2—C21.666 (4)
K1—N1iv2.823 (5)C1—N11.162 (6)
K1—N2v2.885 (4)C2—N21.145 (6)
K1—N1vi2.986 (4)
S1—Ag1—S2126.49 (4)S2—Ag1—S2ii95.29 (3)
S1—Ag1—S1i100.64 (3)S1i—Ag1—S2ii101.75 (4)
S2—Ag1—S1i119.21 (4)N1—C1—S1177.4 (4)
S1—Ag1—S2ii110.78 (4)N2—C2—S2177.6 (4)
Symmetry codes: (i) x1/2, y, z+1/2; (ii) x, y+1, z+1; (iii) x+1, y, z; (iv) x+1/2, y1/2, z; (v) x+1/2, y, z+1/2; (vi) x+1, y1/2, z+1/2; (vii) x+1, y+1, z+1; (viii) x+1/2, y+1/2, z+1.
 

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