research communications
Redetermination of the _{2}Hg(SCN)_{4}
of K^{a}Anorganische Chemie, Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032 Marburg
^{*}Correspondence e-mail: florian.kraus@chemie.uni-marburg.de
Single crystals of K_{2}Hg(SCN)_{4} [dipotassium tetrathiocyanatomercurate(II)] were grown from aqueous solutions of potassium thiocyanate and mercury(II) thiocyanate and studied by single-crystal X-ray diffraction. In comparison with the previously reported structure model [Zvonkova (1952). Zh. Fiz. Khim. 26, 1798–1803], all atoms in the were located, with parameters and fractional coordinates determined to a much higher precision. In the (crystal) structure, the Hg^{II} atom is located on a twofold rotation axis and is coordinated in the form of a distorted tetrahedron by four S atoms of the thiocyanate anions. The K^{+} cation shows a of eight.
Keywords: crystal structure; redetermination; mercury; thiocyanate.
CCDC reference: 1556957
1. Chemical context
In search for suitable educts for fluorination we thought that K_{2}Hg(SCN)_{4} would be a well-suited candidate. Once we had obtained the compound, we noticed that the original (Zvonkova, 1952) was of low precision with the light atoms (C and N) not determined, so we redetermined the to much higher precision and accuracy.
K_{2}Hg(SCN)_{4} was first synthesized in 1901 (Rosenheim & Cohn, 1901) by adding an aqueous solution of potassium thiocyanate to a boiling solution of mercury(II) thiocyanate and crystallization upon cooling to room temperature. The has been known since 1952 (Zvonkova, 1952) and IR spectra were first measured in 1962 (Tramer, 1962). Related compounds of the type A_{2}Hg(SCN)_{4} with A = Rb, Cs, NH_{4}, NMe_{4} are also known (Larbot & Beauchamp, 1973; Tramer, 1962). The Hg^{II} atom in K_{2}Hg(SCN)_{4} is coordinated in the form of a distorted tetrahedron by four S atoms in a fashion similar to the Hg^{II} atom in the structure of CoHg(SCN)_{4} (Jefferey & Rose, 1968). Such tetrahedrally coordinated Hg^{II} atoms are also known, for example, for the halide and pseudo-halide compounds A_{2}HgX_{4}, viz. Cs_{2}HgBr_{4} (Pakhomov et al., 1978; Altermatt et al., 1984; Pinheiro et al., 1998), Cs_{2}HgCl_{4} (Linde et al., 1983; Pakhomov et al. 1992a,b; Bagautdinov & Brown, 2000), Cs_{2}HgI_{4} (Zandbergen et al., 1979; Pakhomov & Fedorov, 1973), K_{2}Hg(CN)_{4} (Gerlach & Powell, 1986; Dickinson, 1922) and Rb_{2}Hg(CN)_{4} (Klüfers et al., 1981).
2. Structural commentary
The ) agree with those obtained previously (a = 11.04, b = 9.22, c = 13.18 Å, β = 106.30°, Z = 4; Zvonkova, 1952). K_{2}Hg(SCN)_{4} crystallizes in the monoclinic in C2/c (No. 15). The Hg^{II} atom is located on a twofold rotation axis (Wyckoff position 4e) and is coordinated in the form of a distorted tetrahedron by four S atoms of the thiocyanate anions (Fig. 1). The S—Hg—S angles are in the range 105.02 (2)–114.67 (3)° and the Hg—S distances are 2.5380 (8) and 2.5550 (7) Å, both in good agreement with the previously reported data (S—Hg—S angle: 102–118°, Hg—S distance: 2.54 (2); Zvonkova, 1952). The Hg—S distance is slightly longer than those of the sixfold-coordinated Hg^{II} atom in Hg(SCN)_{2} [2.381 (6) Å] (Beauchamp & Goutier, 1972) and lies within the range of Hg—S distances [2.3954 (11)–2.7653 (6) Å] for the threefold coordinated Hg^{II} atom in KHg(SCN)_{3} (Weil & Häusler, 2014).
parameters obtained by our room-temperature single-crystal (Table 1As may be expected, the two unique SCN^{−} anions are almost linear [178.0 (3), 178.2 (3)°], and the angles are comparable with those reported for Hg(SCN)_{2} [177.5 (13)°; Beauchamp & Goutier, 1972] or KHg(SCN)_{3} [176.41 (4)–179.8 (3)°; Weil & Häusler, 2014]. The S—C [1.656 (3), 1.665 (3) Å] and C—N [1.153 (5), 1.152 (4) Å] distances are comparable as well [S—C: 1.62 (2), C—N: 1.18 (3) Å] (Beauchamp & Goutier, 1972) [S—C: 1.657 (4)–1.675 (3) Å, C—N: 1.140 (4)–1.145 (5) Å] (Weil & Häusler, 2014). The Hg—S—C angles in the title salt are 98.59 (10) and 97.06 (10)°, respectively. In comparison with the of the Hg^{II} atom and the structural feature of the SCN^{−} anions in CoHg(SCN)_{4} [Hg—S: 2.558–2.614 Å, S—C: 1.635–1.720 Å, C—N: 1.200–1.322 Å, S—Hg—S angles: 105.1 (1), 108.7 (1)°, Hg—S—C angle: 97.3 (5)°] (Jefferey & Rose, 1968), the respective angles and distances of the complex [Hg(SCN)_{4}]^{2−} anion presented here agree well. In total, a [Hg(SCN)_{4}]^{2−} anion is surrounded by twelve potassium atoms.
The K^{+} cation shows a of eight, with disparate bond lengths that can be associated with a [4 + 3 + 1] coordination. Four K—N distances are in the range 2.816 (4)–3.031 (5) Å, three K—S distances are in the range 3.4466 (11)–3.5315 (12) Å and there is one very long K—N distance of 3.793 (5) Å. Therefore, the resulting is of an odd shape. The K^{+} cation is coordinated in total by five [Hg(SCN)_{4}]^{2−} units, three of these in a monodentate manner (two via N atoms and one via the S atom of the thiocyanate anions) and the other two in a bidentate mode (via the N and S atoms of neighboring thiocyanate anions). Overall, a complex three-dimensional framework results. The of the title compound is shown in Fig. 2.
3. Synthesis and crystallization
Potassium tetrathiocyanatomercurate(II) was synthesized by slowly adding a potassium thiocyanate solution (2.076 g, 21.36 mmol in 10 ml H_{2}O) to a boiling solution of mercury(II) thiocyanate (3.176 g, 10.03 mmol in 10 ml H_{2}O). After the formed mercury sulfide had been filtered off through a Büchner funnel, the solution was concentrated on a hot plate until crystallization set in. The crystallized product was collected on a Büchner funnel and the filtrate was allowed to stand at room temperature until crystals of much better quality were obtained. A selected colorless single crystal was investigated by X-ray diffraction. Mercury(II) thiocyanate was prepared as reported previously (Hermes, 1866) using mercury(II) nitrate and potasium thiocyanate and was recrystallized out of ethanol.
4. Refinement
Crystal data, data collection and structure . As a starting model for the structure the atomic coordinates of the previously reported K_{2}Hg(SCN)_{4} structure model were used (Zvonkova, 1952). The positions of the C and N atoms were located from a difference-Fourier map.
details are summarized in Table 1Supporting information
CCDC reference: 1556957
https://doi.org//10.1107/S2056989017009148/wm5399sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org//10.1107/S2056989017009148/wm5399Isup2.hkl
Data collection: X-AREA (Stoe & Cie, 2011); cell
X-AREA (Stoe & Cie, 2011); data reduction: X-RED (Stoe & Cie, 2009); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: DIAMOND (Brandenburg, 2015); software used to prepare material for publication: publCIF (Westrip, 2010).K_{2}Hg(SCN)_{4} | F(000) = 936 |
M_{r} = 511.11 | D_{x} = 2.636 Mg m^{−}^{3} |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
a = 10.8154 (9) Å | Cell parameters from 25154 reflections |
b = 9.3243 (7) Å | θ = 2.9–35.0° |
c = 13.3313 (11) Å | µ = 13.21 mm^{−}^{1} |
β = 106.648 (6)° | T = 293 K |
V = 1288.05 (18) Å^{3} | Block, colourless |
Z = 4 | 0.24 × 0.15 × 0.12 mm |
Stoe IPDS 2T diffractometer | 2710 independent reflections |
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus | 2298 reflections with I > 2σ(I) |
Plane graphite monochromator | R_{int} = 0.043 |
Detector resolution: 6.67 pixels mm^{-1} | θ_{max} = 34.6°, θ_{min} = 2.9° |
rotation method scans | h = −17→17 |
Absorption correction: integration (X-RED32 and X-SHAPE; Stoe & Cie, 2009) | k = −14→14 |
T_{min} = 0.103, T_{max} = 0.344 | l = −21→21 |
14009 measured reflections |
Refinement on F^{2} | Primary atom site location: other |
Least-squares matrix: full | Secondary atom site location: other |
R[F^{2} > 2σ(F^{2})] = 0.024 | w = 1/[σ^{2}(F_{o}^{2}) + (0.022P)^{2} + 1.7P] where P = (F_{o}^{2} + 2F_{c}^{2})/3 |
wR(F^{2}) = 0.053 | (Δ/σ)_{max} = 0.001 |
S = 1.08 | Δρ_{max} = 1.15 e Å^{−}^{3} |
2710 reflections | Δρ_{min} = −0.75 e Å^{−}^{3} |
70 parameters | Extinction correction: SHELXL2014 (Sheldrick, 2015b), Fc^{*}=kFc[1+0.001xFc^{2}λ^{3}/sin(2θ)]^{-1/4} |
0 restraints | Extinction coefficient: 0.0086 (2) |
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 | U_{iso}*/U_{eq} | ||
Hg | 0.0000 | 0.52099 (2) | 0.2500 | 0.03803 (7) | |
K | 0.16185 (7) | 1.04695 (8) | 0.43195 (7) | 0.04817 (17) | |
S1 | 0.10639 (7) | 0.68302 (8) | 0.40531 (6) | 0.03720 (14) | |
S2 | 0.18135 (7) | 0.36527 (10) | 0.22498 (7) | 0.04701 (18) | |
C1 | −0.0130 (3) | 0.6793 (3) | 0.4611 (2) | 0.0332 (5) | |
C2 | 0.3046 (3) | 0.4505 (3) | 0.3055 (3) | 0.0387 (6) | |
N1 | −0.0940 (3) | 0.6801 (3) | 0.5013 (3) | 0.0462 (6) | |
N2 | 0.3926 (3) | 0.5077 (4) | 0.3607 (4) | 0.0615 (9) |
U^{11} | U^{22} | U^{33} | U^{12} | U^{13} | U^{23} | |
Hg | 0.02612 (7) | 0.05275 (11) | 0.03471 (8) | 0.000 | 0.00789 (5) | 0.000 |
K | 0.0336 (3) | 0.0491 (4) | 0.0637 (4) | −0.0053 (3) | 0.0169 (3) | −0.0164 (3) |
S1 | 0.0294 (3) | 0.0399 (3) | 0.0426 (3) | −0.0077 (2) | 0.0107 (2) | −0.0070 (3) |
S2 | 0.0350 (3) | 0.0567 (5) | 0.0486 (4) | 0.0053 (3) | 0.0108 (3) | −0.0162 (3) |
C1 | 0.0307 (11) | 0.0271 (11) | 0.0399 (12) | −0.0003 (9) | 0.0070 (9) | −0.0026 (9) |
C2 | 0.0304 (12) | 0.0385 (15) | 0.0475 (14) | 0.0066 (10) | 0.0115 (10) | 0.0066 (11) |
N1 | 0.0408 (13) | 0.0437 (14) | 0.0586 (17) | −0.0011 (11) | 0.0215 (12) | −0.0039 (12) |
N2 | 0.0346 (14) | 0.0530 (19) | 0.087 (3) | 0.0011 (12) | 0.0023 (14) | 0.0011 (16) |
Hg—S2 | 2.5380 (8) | K—K^{iv} | 4.4669 (15) |
Hg—S2^{i} | 2.5380 (8) | S1—C1 | 1.665 (3) |
Hg—S1^{i} | 2.5550 (7) | S1—K^{v} | 3.5316 (12) |
Hg—S1 | 2.5551 (7) | S2—C2 | 1.656 (3) |
K—N2^{ii} | 2.816 (4) | S2—K^{viii} | 3.4865 (12) |
K—N1^{iii} | 2.823 (3) | C1—N1 | 1.152 (4) |
K—N1^{iv} | 2.860 (3) | C1—K^{iv} | 3.529 (3) |
K—N2^{v} | 3.031 (5) | C2—N2 | 1.153 (5) |
K—C2^{vi} | 3.408 (3) | C2—K^{viii} | 3.408 (3) |
K—C2^{v} | 3.414 (3) | C2—K^{v} | 3.414 (3) |
K—S1 | 3.4466 (11) | N1—K^{ix} | 2.823 (3) |
K—S2^{vi} | 3.4865 (12) | N1—K^{iv} | 2.860 (3) |
K—S1^{v} | 3.5315 (12) | N2—K^{x} | 2.816 (4) |
K—C1^{iv} | 3.529 (3) | N2—K^{v} | 3.031 (5) |
K—K^{vii} | 4.3913 (14) | ||
S2—Hg—S2^{i} | 110.21 (4) | S1—K—C1^{iv} | 131.89 (5) |
S2—Hg—S1^{i} | 114.67 (3) | S2^{vi}—K—C1^{iv} | 161.89 (6) |
S2^{i}—Hg—S1^{i} | 105.02 (2) | S1^{v}—K—C1^{iv} | 121.11 (5) |
S2—Hg—S1 | 105.02 (2) | N2^{ii}—K—K^{vii} | 122.43 (8) |
S2^{i}—Hg—S1 | 114.67 (3) | N1^{iii}—K—K^{vii} | 39.71 (6) |
S1^{i}—Hg—S1 | 107.50 (4) | N1^{iv}—K—K^{vii} | 39.09 (6) |
N2^{ii}—K—N1^{iii} | 161.33 (10) | N2^{v}—K—K^{vii} | 86.73 (7) |
N2^{ii}—K—N1^{iv} | 83.58 (10) | C2^{vi}—K—K^{vii} | 117.52 (6) |
N1^{iii}—K—N1^{iv} | 78.80 (9) | C2^{v}—K—K^{vii} | 70.39 (6) |
N2^{ii}—K—N2^{v} | 80.42 (13) | S1—K—K^{vii} | 159.02 (4) |
N1^{iii}—K—N2^{v} | 100.55 (9) | S2^{vi}—K—K^{vii} | 116.01 (3) |
N1^{iv}—K—N2^{v} | 74.44 (9) | S1^{v}—K—K^{vii} | 97.01 (3) |
N2^{ii}—K—C2^{vi} | 91.55 (12) | C1^{iv}—K—K^{vii} | 53.40 (5) |
N1^{iii}—K—C2^{vi} | 94.70 (8) | N2^{ii}—K—K^{iv} | 41.99 (10) |
N1^{iv}—K—C2^{vi} | 128.94 (9) | N1^{iii}—K—K^{iv} | 136.17 (7) |
N2^{v}—K—C2^{vi} | 154.57 (9) | N1^{iv}—K—K^{iv} | 75.38 (6) |
N2^{ii}—K—C2^{v} | 98.21 (12) | N2^{v}—K—K^{iv} | 38.43 (7) |
N1^{iii}—K—C2^{v} | 81.16 (8) | C2^{vi}—K—K^{iv} | 129.03 (5) |
N1^{iv}—K—C2^{v} | 68.68 (8) | C2^{v}—K—K^{iv} | 56.66 (5) |
N2^{v}—K—C2^{v} | 19.47 (8) | S1—K—K^{iv} | 73.46 (2) |
C2^{vi}—K—C2^{v} | 161.02 (7) | S2^{vi}—K—K^{iv} | 136.14 (3) |
N2^{ii}—K—S1 | 72.82 (7) | S1^{v}—K—K^{iv} | 97.61 (3) |
N1^{iii}—K—S1 | 125.84 (7) | C1^{iv}—K—K^{iv} | 58.43 (5) |
N1^{iv}—K—S1 | 148.83 (6) | K^{vii}—K—K^{iv} | 107.42 (3) |
N2^{v}—K—S1 | 81.66 (7) | C1—S1—Hg | 97.06 (10) |
C2^{vi}—K—S1 | 72.91 (5) | C1—S1—K | 96.25 (9) |
C2^{v}—K—S1 | 94.40 (6) | Hg—S1—K | 133.66 (3) |
N2^{ii}—K—S2^{vi} | 111.59 (10) | C1—S1—K^{v} | 102.56 (10) |
N1^{iii}—K—S2^{vi} | 80.81 (6) | Hg—S1—K^{v} | 102.38 (3) |
N1^{iv}—K—S2^{vi} | 146.21 (6) | K—S1—K^{v} | 117.55 (2) |
N2^{v}—K—S2^{vi} | 136.13 (7) | C2—S2—Hg | 98.59 (10) |
C2^{vi}—K—S2^{vi} | 27.76 (5) | C2—S2—K^{viii} | 73.50 (11) |
C2^{v}—K—S2^{vi} | 133.75 (5) | Hg—S2—K^{viii} | 109.15 (3) |
S1—K—S2^{vi} | 63.89 (2) | N1—C1—S1 | 178.0 (3) |
N2^{ii}—K—S1^{v} | 127.71 (8) | N1—C1—K^{iv} | 46.43 (18) |
N1^{iii}—K—S1^{v} | 68.47 (7) | S1—C1—K^{iv} | 131.85 (12) |
N1^{iv}—K—S1^{v} | 123.33 (7) | N2—C2—S2 | 178.2 (3) |
N2^{v}—K—S1^{v} | 68.09 (7) | N2—C2—K^{viii} | 100.5 (3) |
C2^{vi}—K—S1^{v} | 99.48 (6) | S2—C2—K^{viii} | 78.74 (12) |
C2^{v}—K—S1^{v} | 61.72 (5) | N2—C2—K^{v} | 61.1 (3) |
S1—K—S1^{v} | 62.45 (2) | S2—C2—K^{v} | 119.82 (14) |
S2^{vi}—K—S1^{v} | 72.06 (2) | K^{viii}—C2—K^{v} | 160.38 (10) |
N2^{ii}—K—C1^{iv} | 71.53 (9) | C1—N1—K^{ix} | 127.6 (2) |
N1^{iii}—K—C1^{iv} | 92.39 (7) | C1—N1—K^{iv} | 116.6 (2) |
N1^{iv}—K—C1^{iv} | 16.96 (7) | K^{ix}—N1—K^{iv} | 101.20 (9) |
N2^{v}—K—C1^{iv} | 61.48 (8) | C2—N2—K^{x} | 149.3 (3) |
C2^{vi}—K—C1^{iv} | 138.43 (8) | C2—N2—K^{v} | 99.4 (3) |
C2^{v}—K—C1^{iv} | 60.50 (7) | K^{x}—N2—K^{v} | 99.58 (13) |
Symmetry codes: (i) −x, y, −z+1/2; (ii) x−1/2, y+1/2, z; (iii) x+1/2, y+1/2, z; (iv) −x, −y+2, −z+1; (v) −x+1/2, −y+3/2, −z+1; (vi) −x+1/2, y+1/2, −z+1/2; (vii) −x+1/2, −y+5/2, −z+1; (viii) −x+1/2, y−1/2, −z+1/2; (ix) x−1/2, y−1/2, z; (x) x+1/2, y−1/2, z. |
Acknowledgements
FK thanks the DFG for his Heisenberg professorship, Dr Harms for X-ray measurement time and Julia Hassler for the sample preparation.
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