Crystal structure of K[Hg(SCN)₃] – a redetermination

The crystal structure of the room-temperature modification of K[Hg(SCN)₃], potassium tri­thio­cyanato­mercurate(II), was redetermined based on modern CCD data. In comparison with the previous report [Zhdanov & Sanadze (1952). Zh. Fiz. Khim. 26, 469–478], reliability factors, standard deviations of lattice parameters and atomic coordinates, as well as anisotropic displacement parameters, were revealed for all atoms. The higher precision and accuracy of the model is, for example, reflected by the Hg—S bond lengths of 2.3954 (11), 2.4481 (8) and 2.7653 (6) Å in comparison with values of 2.24, 2.43 and 2.77 Å. All atoms in the crystal structure are located on mirror planes. The Hg²⁺ cation is surrounded by four S atoms in a seesaw shape [S—Hg—S angles range from 94.65 (2) to 154.06 (3)°]. The HgS₄ polyhedra share a common S atom, building up chains extending parallel to [010]. All S atoms of the resulting ¹_∞[HgS_2/1S_2/2] chains are also part of SCN⁻ anions that link these chains with the K⁺ cations into a three-dimensional network. The K—N bond lengths of the distorted KN₇ polyhedra lie between 2.926 (2) and 3.051 (3) Å.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](N-C) = 0.005 Å
• R factor = 0.028
• wR factor = 0.062
• Data-to-parameter ratio = 55.4

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT029_ALERT_3_B _diffrn_measured_fraction_theta_full Low .......      0.943 Note

Alert level C
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....        2.3 Note
PLAT906_ALERT_3_C Large K value in the Analysis of Variance ......      2.179 Check
PLAT975_ALERT_2_C Check Calcd Residual Density  0.85A From      N2       0.40 eA-3
PLAT976_ALERT_2_C Check Calcd Residual Density  0.96A From      N1      -0.48 eA-3

Alert level G
PLAT004_ALERT_5_G Polymeric Structure Found with Dimension .......          2 Info
PLAT005_ALERT_5_G No _iucr_refine_instructions_details  in the CIF     Please Do !
PLAT040_ALERT_1_G No H-atoms in this Carbon Containing Compound ..     Please Check
PLAT158_ALERT_4_G The Input Unitcell is NOT Standard/Reduced .....     Please Check
PLAT199_ALERT_1_G Reported _cell_measurement_temperature ..... (K)        293 Check
PLAT200_ALERT_1_G Reported   _diffrn_ambient_temperature ..... (K)        293 Check
PLAT230_ALERT_2_G Hirshfeld Test Diff for    S1     --  C1      ..        5.2 su
PLAT232_ALERT_2_G Hirshfeld Test Diff (M-X)  Hg1    --  S1      ..        6.0 su
PLAT232_ALERT_2_G Hirshfeld Test Diff (M-X)  Hg1    --  S2      ..       38.0 su
PLAT910_ALERT_3_G Missing # of FCF Reflections Below Th(Min) .....          3 Why ?
PLAT912_ALERT_4_G Missing # of FCF Reflections Above STh/L=  0.600        219 Note

   0 ALERT level A = Most likely a serious problem - resolve or explain
   1 ALERT level B = A potentially serious problem, consider carefully
   4 ALERT level C = Check. Ensure it is not caused by an omission or oversight
  11 ALERT level G = General information/check it is not something unexpected

   3 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   6 ALERT type 2 Indicator that the structure model may be wrong or deficient
   3 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   2 ALERT type 5 Informative message, check

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Related literature

K[Hg(SCN)₃] has been determined originally in the space group P2₁/m with Z = 8, based on room-temperature data (Zhdanov & Sanadze, 1952). A subsequent redetermination revealed a doubled unit cell in P2₁/n, Z = 4, based on intensity data measured at 150 K (Bowmaker et al., 1998). However, there is no report on an apparent phase transition of K[Hg(SCN)₃] between these two temperatures. For symmetry relationships between crystal structures, see: Müller (2013).

S1. Experimental

Hg(SCN)₂ (0.5 g) was dissolved under heating in a water–ethanol mixture (1:1 v/v) to which KSCN (0.1 g) was added. After one week, colourless crystals with a lath-like form were obtained from the remaining solution.

S2. Refinement

For better comparison with the previous determination by Zhdanov & Sanadze (1952), the original nonreduced cell setting as well as the atom labelling and the atomic coordinates were used as starting parameters for the refinement.

Bowmaker et al. (1998) reported a doubled unit cell for K[Hg(SCN)₃] with a = 11.9119 (3), b = 4.0201 (1), c = 18.7095 (3) Å, β = 91.852 (1)°, P2₁/n, Z = 4. However, no superstructure reflections were found in the current redetermination at 293 K, while Bowmaker et al. (1998) used intensity data measured at 150 K. Therefore it appears likely that K[Hg(SCN)₃] has a phase transition between these two temperatures. The two unit cells of the room-temperature phase in P2₁/m and the low-temperature phase in P2₁/n are related by the matix (101,010,101), revealing a klassengleiche symmetry reduction of index 2 (Müller, 2013).

The highest and lowest electron densities are found 0.66 and 0.28 Å, respectively, from atom S3.

Computing details

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS for Windows (Dowty, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures

Fig. 1. The crystal structure of K[Hg(SCN)3] in a projection along [010]. Displacement ellipsoids are drawn at the 90% probability level. Colour code: Hg green, S yellow, C blue, N magenta, K grey. The HgS4 polyhedron is shown in red.

Potassium [trithiocyanatomercurate(II)]

Crystal data

K[Hg(NCS)3]	F(000) = 372
Mr = 413.93	Dx = 3.005 Mg m^−3
Monoclinic, P21/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yb	Cell parameters from 4570 reflections
a = 11.2727 (11) Å	θ = 3.4–33.7°
b = 4.0775 (4) Å	µ = 17.90 mm^−1
c = 10.9764 (10) Å	T = 293 K
β = 114.951 (4)°	Lath, colourless
V = 457.44 (8) Å^3	0.30 × 0.06 × 0.04 mm
Z = 2

Data collection

Bruker APEXII CCD diffractometer	3765 independent reflections
Radiation source: fine-focus sealed tube	2358 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.032
ω and ϕ scans	θmax = 44.4°, θmin = 3.4°
Absorption correction: multi-scan (SADABS; Bruker, 2008)	h = −19→22
Tmin = 0.226, Tmax = 0.504	k = −7→7
11940 measured reflections	l = −21→18

Refinement

Refinement on F^2	Primary atom site location: isomorphous structure methods
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + (0.0218P)^2 + 0.0583P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.028	(Δ/σ)max = 0.001
wR(F^2) = 0.062	Δρmax = 1.27 e Å^−3
S = 1.03	Δρmin = −1.33 e Å^−3
3765 reflections	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
68 parameters	Extinction coefficient: 0.0219 (8)
0 restraints

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Hg1	0.145383 (12)	0.2500	0.725128 (12)	0.03813 (6)
K1	0.59433 (8)	0.7500	0.71536 (7)	0.03802 (15)
S1	0.12455 (7)	0.2500	0.49391 (8)	0.03495 (17)
S2	0.32808 (7)	0.7500	0.80993 (8)	0.03121 (14)
S3	0.06157 (10)	0.2500	0.89262 (10)	0.0704 (4)
C1	0.2848 (3)	0.2500	0.5314 (3)	0.0313 (6)
C2	0.3579 (3)	0.7500	0.9719 (3)	0.0312 (6)
C3	0.9019 (4)	0.2500	0.7977 (4)	0.0357 (6)
N1	0.3940 (3)	0.2500	0.5574 (3)	0.0477 (8)
N2	0.6210 (4)	0.2500	0.9165 (3)	0.0500 (8)
N3	0.7909 (4)	0.2500	0.7382 (4)	0.0601 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Hg1	0.03374 (7)	0.05407 (10)	0.03323 (8)	0.000	0.02060 (5)	0.000
K1	0.0377 (3)	0.0421 (4)	0.0364 (3)	0.000	0.0177 (3)	0.000
S1	0.0247 (3)	0.0544 (5)	0.0247 (3)	0.000	0.0094 (3)	0.000
S2	0.0292 (3)	0.0372 (4)	0.0296 (3)	0.000	0.0147 (3)	0.000
S3	0.0341 (4)	0.1516 (14)	0.0307 (4)	0.000	0.0188 (4)	0.000
C1	0.0334 (14)	0.0392 (16)	0.0243 (12)	0.000	0.0150 (11)	0.000
C2	0.0268 (12)	0.0344 (15)	0.0309 (14)	0.000	0.0107 (11)	0.000
C3	0.0376 (15)	0.0406 (17)	0.0398 (16)	0.000	0.0269 (13)	0.000
N1	0.0329 (14)	0.075 (2)	0.0379 (15)	0.000	0.0175 (12)	0.000
N2	0.0529 (19)	0.064 (2)	0.0292 (14)	0.000	0.0134 (13)	0.000
N3	0.0394 (17)	0.096 (3)	0.050 (2)	0.000	0.0248 (15)	0.000

Geometric parameters (Å, º)

Hg1—S3	2.3954 (11)	K1—K1^iii	4.7485 (14)
Hg1—S1	2.4481 (8)	S1—C1	1.675 (3)
Hg1—S2	2.7653 (6)	S2—C2	1.664 (3)
Hg1—S2^i	2.7653 (6)	S2—Hg1^ii	2.7653 (6)
K1—N2^ii	2.926 (2)	S3—C3^iv	1.657 (4)
K1—N2	2.926 (2)	C1—N1	1.140 (4)
K1—N3^ii	2.943 (3)	C1—K1^iii	3.508 (3)
K1—N3	2.943 (3)	C2—N2^v	1.145 (5)
K1—N1	2.993 (2)	C3—N3	1.141 (6)
K1—N1^ii	2.993 (2)	C3—S3^vi	1.657 (4)
K1—N1^iii	3.051 (3)	N1—K1^i	2.993 (2)
K1—C1^iii	3.508 (3)	N1—K1^iii	3.051 (3)
K1—S2	3.5657 (12)	N2—C2^v	1.145 (5)
K1—K1^i	4.0775 (4)	N2—K1^i	2.926 (2)
K1—K1^ii	4.0775 (4)	N3—K1^i	2.943 (3)
S3—Hg1—S1	154.06 (3)	C1^iii—K1—K1^i	90.0
S3—Hg1—S2	102.74 (2)	S2—K1—K1^i	90.0
S1—Hg1—S2	94.65 (2)	N2^ii—K1—K1^ii	45.83 (5)
S3—Hg1—S2^i	102.74 (2)	N2—K1—K1^ii	134.17 (5)
S1—Hg1—S2^i	94.65 (2)	N3^ii—K1—K1^ii	46.15 (5)
S2—Hg1—S2^i	95.00 (2)	N3—K1—K1^ii	133.85 (5)
N2^ii—K1—N2	88.34 (9)	N1—K1—K1^ii	132.94 (4)
N2^ii—K1—N3^ii	67.60 (10)	N1^ii—K1—K1^ii	47.06 (4)
N2—K1—N3^ii	125.76 (10)	N1^iii—K1—K1^ii	90.0
N2^ii—K1—N3	125.76 (10)	C1^iii—K1—K1^ii	90.0
N2—K1—N3	67.60 (10)	S2—K1—K1^ii	90.0
N3^ii—K1—N3	87.70 (10)	K1^i—K1—K1^ii	180.00 (5)
N2^ii—K1—N1	136.39 (10)	N2^ii—K1—K1^iii	155.60 (6)
N2—K1—N1	76.98 (8)	N2—K1—K1^iii	108.20 (5)
N3^ii—K1—N1	151.42 (11)	N3^ii—K1—K1^iii	112.78 (8)
N3—K1—N1	86.24 (8)	N3—K1—K1^iii	78.02 (8)
N2^ii—K1—N1^ii	76.98 (8)	N1—K1—K1^iii	38.66 (6)
N2—K1—N1^ii	136.39 (10)	N1^ii—K1—K1^iii	78.70 (6)
N3^ii—K1—N1^ii	86.24 (7)	N1^iii—K1—K1^iii	37.79 (4)
N3—K1—N1^ii	151.42 (11)	C1^iii—K1—K1^iii	52.26 (4)
N1—K1—N1^ii	85.87 (8)	S2—K1—K1^iii	102.20 (3)
N2^ii—K1—N1^iii	135.00 (5)	K1^i—K1—K1^iii	64.574 (8)
N2—K1—N1^iii	135.00 (5)	K1^ii—K1—K1^iii	115.426 (8)
N3^ii—K1—N1^iii	75.01 (9)	C1—S1—Hg1	97.08 (11)
N3—K1—N1^iii	75.01 (9)	C2—S2—Hg1	98.38 (7)
N1—K1—N1^iii	76.45 (8)	C2—S2—Hg1^ii	98.38 (7)
N1^ii—K1—N1^iii	76.45 (8)	Hg1—S2—Hg1^ii	95.00 (2)
N2^ii—K1—C1^iii	129.27 (7)	C2—S2—K1	119.70 (11)
N2—K1—C1^iii	129.27 (7)	Hg1—S2—K1	120.06 (2)
N3^ii—K1—C1^iii	62.76 (8)	Hg1^ii—S2—K1	120.06 (2)
N3—K1—C1^iii	62.76 (8)	C3^iv—S3—Hg1	101.12 (13)
N1—K1—C1^iii	89.79 (8)	N1—C1—S1	179.8 (3)
N1^ii—K1—C1^iii	89.79 (8)	N1—C1—K1^iii	57.5 (2)
N1^iii—K1—C1^iii	18.38 (8)	S1—C1—K1^iii	122.68 (14)
N2^ii—K1—S2	67.14 (8)	N2^v—C2—S2	179.7 (3)
N2—K1—S2	67.14 (8)	N3—C3—S3^vi	176.4 (4)
N3^ii—K1—S2	132.15 (6)	C1—N1—K1	128.00 (14)
N3—K1—S2	132.15 (6)	C1—N1—K1^i	128.00 (14)
N1—K1—S2	69.32 (6)	K1—N1—K1^i	85.87 (8)
N1^ii—K1—S2	69.32 (6)	C1—N1—K1^iii	104.1 (2)
N1^iii—K1—S2	132.49 (6)	K1—N1—K1^iii	103.55 (8)
C1^iii—K1—S2	150.86 (6)	K1^i—N1—K1^iii	103.55 (8)
N2^ii—K1—K1^i	134.17 (5)	C2^v—N2—K1^i	135.73 (5)
N2—K1—K1^i	45.83 (5)	C2^v—N2—K1	135.73 (5)
N3^ii—K1—K1^i	133.85 (5)	K1^i—N2—K1	88.34 (9)
N3—K1—K1^i	46.15 (5)	C3—N3—K1^i	130.79 (15)
N1—K1—K1^i	47.06 (4)	C3—N3—K1	130.79 (15)
N1^ii—K1—K1^i	132.94 (4)	K1^i—N3—K1	87.70 (10)
N1^iii—K1—K1^i	90.0

Symmetry codes: (i) x, y−1, z; (ii) x, y+1, z; (iii) −x+1, −y+1, −z+1; (iv) x−1, y, z; (v) −x+1, −y+1, −z+2; (vi) x+1, y, z.