Potassium tetra­cyanidoaurate(III) monohydrate: a redetermination

Matsushita, N.; Noguchi, W.; Tanaka, R.

doi:10.1107/S2414314617003820

metal-organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 2| Part 3| March 2017| x170382

https://doi.org/10.1107/S2414314617003820

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Potassium tetracyanidoaurate(III) monohydrate: a redetermination

Nobuyuki Matsushita,^a ^* Wataru Noguchi ^b and Rikako Tanaka ^a

^aDepartment of Chemistry & Research Center for Smart Molecules, Rikkyo University, Nishi-Ikebukuro 3-34-1, Toshima-ku, 171-8501 Tokyo, Japan, and ^bDepartment of Chemistry, Rikkyo University, Nishi-Ikebukuro 3-34-1, Toshima-ku, 171-8501 Tokyo, Japan
^*Correspondence e-mail: cnmatsu@rikkyo.ac.jp

Edited by M. Weil, Vienna University of Technology, Austria (Received 6 March 2017; accepted 9 March 2017; online 14 March 2017)

The structure of the title metal complex salt, K[Au(CN)₄]·H₂O, has been redetermined using X-ray diffraction data at 173 K in order to improve the precision. The previous determination was based on neutron diffraction data [Bertinotti & Bertinotti (1970). Acta Cryst. B26, 422–428]. The title compound crystallizes in the space group P2₁2₁2₁ with one potassium cation, one [Au(CN)₄]⁻ anion and one water molecule in the asymmetric unit. The Au^III atom lies on a general position and has an almost square-planar coordination sphere defined by four cyanide ligands. Interactions between the potassium cation and N atoms of the complex anion, as well as O—H⋯N hydrogen bonds, lead to the formation of a three-dimensional framework structure.

Keywords: crystal structure; redetermination; tetracyanidoaurate(III); square-planar coordination.

CCDC reference: 1536909

Structure description

Potassium tetracyanidoaurate(III) monohydrate, K[Au(CN)₄]·H₂O, is one of the typical starting compounds for preparation of various tetracyanidoaurate(III) salts. The crystal structure of K[Au(CN)₄]·H₂O has already been determined by neutron diffraction (Bertinotti & Bertinotti, 1970 ). However, because of the need for more precise structural data, we have redetermined the crystal structure using X-ray diffraction data at 173 K. The redetermination of the title salt confirms the previous model but shows an improvement with respect to the precision on bond lengths and angles, with respective standard uncertainties decreased to about one half to one third of those of the previous determination by neutron diffraction. In addition, in the current study all atoms were refined with anisotropic displacement parameters and the absolute structure was determined.

The components of the title salt are displayed in Fig. 1. The asymmetric unit comprises one potassium cation, one [Au(CN)₄]⁻ anion and one water molecule. The Au^III atom of the [Au(CN)₄]⁻ anion is coordinated by four C atoms of four cyanido ligands in an almost square-planar configuration. The r.m.s. deviation of the least-squares plane formed by atoms Au, C1, C2, C3, C4, N1, N2, N3 and N4 is 0.0265 Å. The Au—C [1.998 (4)–2.007 (4) Å] and C≡N [1.138 (5)–1.146 (5) Å] bond lengths, C—Au—C_trans [178.63 (18), 179.39 (17)°], C—Au—C_cis [89.22 (16)–90.75 (17)°] and Au—C—N [177.3 (4)–179.7 (4)°] bond angles are consistent with values reported by Geisheimer et al. (2011 ) for the [Au(CN)₄]⁻ anion in related compounds: [N(C₄H₉)₄][Au(CN)₄] [Au—C = 1.992 (3)–2.002 (3) Å, C≡N = 1.139 (5)–1.148 (5) Å, C—Au—C_trans = 178.03 (12), 179.25 (13)°, C—Au—C_cis = 89.44 (13)–90.49 (14)°, Au—C—N = 177.0 (3)–178.4 (3)°]; [As(C₆H₅)₄][Au(CN)₄] [Au—C = 1.985 (2)–1.996 (2) Å, C≡N = 1.140 (3)–1.150 (3) Å, C—Au—C_trans = 179.35 (9), 179.74 (9)°, C—Au—C_cis = 89.41 (10)–90.75 (9)°, Au—C—N = 177.8 (2)–179.7 (3)°]; [N(P(C₆H₅)₃)₂][Au(CN)₄] [Au—C = 1.987 (6)–1.997 (5) Å, C≡N = 1.118 (5)–1.132 (6) Å, C—Au—C_trans = 179.10 (19), 179.47 (18)°, C—Au—C_cis = 88.85 (18)–91.00 (19)°, Au—C—N = 177.7 (6)–179.4 (6)°].

Figure 1
The asymmetric unit of the title salt, showing the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level for non-H atoms.

In the crystal, the potassium cation exhibits a coordination number of eight and is surrounded by six N atoms of the cyanido ligands [K⋯N = 2.891 (4)–3.431 (4) Å] and two O atoms of water molecules [K⋯O = 2.804 (3), 2.886 (3) Å] (Fig. 2). Two O—H⋯N hydrogen bonds between the water molecule of crystallization and the [Au(CN)₄]⁻ anion further stabilize the crystal packing of the title salt (Fig. 3, Table 1).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O—H2⋯N1ⁱ	0.84	2.32	3.157 (5)	178
O—H1⋯N2ⁱⁱ	0.84	2.27	2.952 (5)	139
Symmetry codes: (i) $[-x+{\script{3\over 2}}, -y+1, z-{\script{1\over 2}}]$ ; (ii) $[-x+2, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Figure 2
The environment of the K⁺ cation, showing the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Orange dashed lines represent short contacts between the potassium ion and surrounding atoms. [Symmetry codes: (iii) −x + 1, y + $[{1\over 2}]$ , −z + $[{1\over 2}]$ ; (vi) −x + $[{1\over 2}]$ , −y + 1, z + $[{1\over 2}]$ ; (vii) −x + 1, y − $[{1\over 2}]$ , −z + $[{1\over 2}]$ ; (viii) −x + $[{3\over 2}]$ , −y + 1, z + $[{1\over 2}]$ ; (ix) x − $[{1\over 2}]$ , −y + $[{1\over 2}]$ , −z + 1; (x) x − 1, y, z.]

Figure 3
The crystal packing of the title salt, viewed along the b axis. Light-blue dashed lines represent the hydrogen bonds. Orange solid lines indicate the unit cell.

Synthesis and crystallization

To an aqueous solution of H[AuCl₄]·4H₂O (2.007 g) neutralized by an aqueous solution of KOH was added an aqueous solution of KCN (1.286 g) at room temperature under stirring. The colour of the solution also changed immediately from yellow to colourless just after the addition. Slow evaporation of the solution gave colourless platelet single crystals.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. In the final refinements, five reflections, (0 1 23), (0 3 23), (1 0 24), ( $[\overline{1}]$ 6 20) and (1 6 20), were omitted due to poor agreements between observed and calculated intensities. The maximum and minimum electron density peaks are located 0.75 and 0.75 Å, respectively, from the Au atom.

Table 2
Experimental details

Crystal data
Chemical formula	K[Au(CN)₄]·H₂O
M_r	358.16
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	173
a, b, c (Å)	6.6460 (7), 7.0733 (8), 17.4356 (19)
V (Å³)	819.63 (15)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	18.40
Crystal size (mm)	0.30 × 0.30 × 0.20

Data collection
Diffractometer	Rigaku R-AXIS RAPID imaging-plate
Absorption correction	Multi-scan (ABSCOR; Higashi, 1995 )
T_min, T_max	0.437, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	17391, 2828, 2666
R_int	0.045
(sin θ/λ)_max (Å⁻¹)	0.745

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.015, 0.034, 1.03
No. of reflections	2828
No. of parameters	101
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	1.44, −1.09
Absolute structure	Flack x determined using 1076 quotients [(I⁺)−(I⁻)]/[(I⁺)+(I⁻)] (Parsons et al., 2013 )
Absolute structure parameter	−0.006 (6)
Computer programs: RAPID-AUTO (Rigaku, 2006 ), SHELXT (Sheldrick, 2015a ), DIAMOND (Brandenburg, 2017 ) and SHELXL2014 (Sheldrick, 2015b ) and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 1536909

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S2414314617003820/wm4042sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314617003820/wm4042Isup2.hkl

checkCIF report

Computing details top

Data collection: RAPID-AUTO (Rigaku, 2006); cell refinement: RAPID-AUTO (Rigaku, 2006); data reduction: RAPID-AUTO (Rigaku, 2006); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: DIAMOND (Brandenburg, 2017); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015b) and publCIF (Westrip, 2010).

Potassium tetracyanidoaurate(III) monohydrate top

Crystal data top

K[Au(CN)₄]·H₂O	D_x = 2.902 Mg m⁻³
M_r = 358.16	Mo Kα radiation, λ = 0.71075 Å
Orthorhombic, P2₁2₁2₁	Cell parameters from 8740 reflections
a = 6.6460 (7) Å	θ = 3.1–31.9°
b = 7.0733 (8) Å	µ = 18.40 mm⁻¹
c = 17.4356 (19) Å	T = 173 K
V = 819.63 (15) Å³	Platelet, colorless
Z = 4	0.30 × 0.30 × 0.20 mm
F(000) = 640

Data collection top

Rigaku R-AXIS RAPID imaging-plate diffractometer	2828 independent reflections
Radiation source: X-ray sealed tube	2666 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.045
Detector resolution: 10.00 pixels mm^-1	θ_max = 32.0°, θ_min = 3.1°
ω scans	h = −9→9
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	k = −10→10
T_min = 0.437, T_max = 1.000	l = −25→23
17391 measured reflections

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.015	w = 1/[σ²(F_o²) + (0.0069P)²] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.034	(Δ/σ)_max = 0.001
S = 1.03	Δρ_max = 1.44 e Å⁻³
2828 reflections	Δρ_min = −1.09 e Å⁻³
101 parameters	Extinction correction: SHELXL2014 (Sheldrick, 2015b), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0093 (3)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack x determined using 1076 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013)
Secondary atom site location: difference Fourier map	Absolute structure parameter: −0.006 (6)

Special details top

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.

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

- 2.5906 (0.0057) x + 6.3743 (0.0030) y + 3.3049 (0.0146) z = 2.5384 (0.0067)

* 0.0043 (0.0013) Au * -0.0216 (0.0038) C1 * 0.0054 (0.0039) C2 * -0.0097 (0.0037) C3 * 0.0245 (0.0037) C4 * -0.0325 (0.0030) N1 * 0.0402 (0.0031) N2 * -0.0400 (0.0030) N3 * 0.0293 (0.0030) N4

Rms deviation of fitted atoms = 0.0265

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Au	0.75839 (2)	0.57191 (2)	0.26080 (2)	0.01211 (5)
C1	0.6473 (6)	0.4715 (7)	0.3595 (2)	0.0172 (9)
C2	1.0114 (6)	0.6470 (7)	0.3147 (2)	0.0177 (8)
C3	0.8687 (6)	0.6664 (6)	0.1607 (2)	0.0163 (8)
C4	0.5035 (6)	0.4994 (6)	0.2069 (2)	0.0165 (8)
N1	0.5844 (5)	0.4150 (6)	0.4160 (2)	0.0214 (8)
N2	1.1526 (6)	0.6928 (7)	0.3475 (2)	0.0255 (9)
N3	0.9262 (6)	0.7151 (6)	0.1027 (2)	0.0220 (8)
N4	0.3604 (5)	0.4584 (6)	0.1752 (2)	0.0228 (8)
K	0.23731 (16)	0.46003 (12)	0.51708 (4)	0.02024 (17)
O	0.6252 (5)	0.3372 (5)	0.01812 (17)	0.0252 (7)
H1	0.6663	0.3529	0.0632	0.038*
H2	0.7007	0.4050	−0.0090	0.038*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Au	0.01349 (7)	0.01157 (7)	0.01126 (8)	−0.00070 (7)	0.00035 (6)	−0.00005 (4)
C1	0.0172 (18)	0.018 (2)	0.017 (2)	0.0028 (16)	−0.0013 (15)	−0.0003 (16)
C2	0.0190 (19)	0.015 (2)	0.0191 (19)	0.0003 (17)	0.0032 (16)	0.0007 (17)
C3	0.0159 (18)	0.016 (2)	0.0173 (19)	0.0017 (16)	0.0008 (15)	−0.0012 (16)
C4	0.0193 (19)	0.015 (2)	0.0151 (19)	0.0006 (16)	0.0010 (15)	0.0038 (16)
N1	0.0222 (17)	0.025 (2)	0.0169 (18)	0.0003 (18)	0.0017 (13)	0.0020 (16)
N2	0.0248 (19)	0.026 (2)	0.0257 (19)	−0.0061 (17)	−0.0049 (16)	−0.0004 (18)
N3	0.0233 (18)	0.024 (2)	0.0189 (18)	−0.0015 (17)	0.0023 (14)	0.0012 (17)
N4	0.0215 (17)	0.024 (2)	0.0228 (19)	−0.0051 (16)	−0.0039 (14)	0.0029 (16)
K	0.0197 (4)	0.0224 (4)	0.0186 (4)	0.0006 (5)	0.0028 (4)	−0.0012 (3)
O	0.0252 (15)	0.031 (2)	0.0194 (15)	0.0023 (13)	0.0014 (12)	0.0035 (14)

Geometric parameters (Å, º) top

Au—C2	1.998 (4)	K—O^vi	2.804 (3)
Au—C1	2.002 (4)	K—Oⁱⁱⁱ	2.886 (4)
Au—C4	2.003 (4)	K—N4^vi	2.891 (4)
Au—C3	2.007 (4)	K—N3^vii	2.923 (4)
C1—N1	1.143 (5)	K—N3^viii	2.961 (4)
C2—N2	1.146 (5)	K—N1^ix	3.071 (4)
C3—N3	1.135 (5)	K—N2^x	3.431 (4)
C4—N4	1.138 (5)	K—Kⁱ	4.4972 (12)
N1—K	2.920 (4)	K—K^ix	4.4972 (12)
N1—Kⁱ	3.071 (4)	O—K^v	2.804 (3)
N2—Kⁱⁱ	3.431 (4)	O—K^vii	2.886 (3)
N3—Kⁱⁱⁱ	2.923 (4)	O—H1	0.8400
N3—K^iv	2.961 (4)	O—H2	0.8400
N4—K^v	2.891 (4)

C2—Au—C1	90.01 (16)	N4^vi—K—N1^ix	74.67 (11)
C2—Au—C4	179.39 (17)	N1—K—N1^ix	113.35 (8)
C1—Au—C4	90.03 (17)	N3^vii—K—N1^ix	68.68 (11)
C2—Au—C3	90.75 (17)	N3^viii—K—N1^ix	72.36 (10)
C1—Au—C3	178.63 (18)	O^vi—K—N2^x	67.62 (9)
C4—Au—C3	89.22 (16)	Oⁱⁱⁱ—K—N2^x	54.90 (9)
N1—C1—Au	179.7 (4)	N4^vi—K—N2^x	133.59 (12)
N2—C2—Au	177.7 (4)	N1—K—N2^x	70.24 (10)
N3—C3—Au	177.3 (4)	N3^vii—K—N2^x	66.90 (11)
N4—C4—Au	178.9 (4)	N3^viii—K—N2^x	139.40 (10)
C1—N1—K	140.5 (3)	N1^ix—K—N2^x	133.45 (10)
C1—N1—Kⁱ	120.6 (3)	O^vi—K—Kⁱ	166.83 (8)
K—N1—Kⁱ	97.27 (11)	Oⁱⁱⁱ—K—Kⁱ	110.40 (7)
C2—N2—Kⁱⁱ	115.4 (3)	N4^vi—K—Kⁱ	115.09 (9)
C3—N3—Kⁱⁱⁱ	133.8 (3)	N1—K—Kⁱ	42.63 (8)
C3—N3—K^iv	125.2 (3)	N3^vii—K—Kⁱ	77.79 (8)
Kⁱⁱⁱ—N3—K^iv	99.69 (11)	N3^viii—K—Kⁱ	39.84 (7)
C4—N4—K^v	126.9 (3)	N1^ix—K—Kⁱ	73.99 (8)
O^vi—K—Oⁱⁱⁱ	78.50 (5)	N2^x—K—Kⁱ	108.91 (7)
O^vi—K—N4^vi	72.47 (10)	O^vi—K—K^ix	72.78 (7)
Oⁱⁱⁱ—K—N4^vi	95.14 (11)	Oⁱⁱⁱ—K—K^ix	144.74 (7)
O^vi—K—N1	137.61 (11)	N4^vi—K—K^ix	95.29 (8)
Oⁱⁱⁱ—K—N1	73.89 (11)	N1—K—K^ix	115.57 (9)
N4^vi—K—N1	140.78 (11)	N3^vii—K—K^ix	40.46 (8)
O^vi—K—N3^vii	89.34 (10)	N3^viii—K—K^ix	110.40 (9)
Oⁱⁱⁱ—K—N3^vii	120.90 (10)	N1^ix—K—K^ix	40.10 (7)
N4^vi—K—N3^vii	135.75 (11)	N2^x—K—K^ix	94.69 (7)
N1—K—N3^vii	78.33 (10)	Kⁱ—K—K^ix	95.28 (3)
O^vi—K—N3^viii	149.29 (10)	K^v—O—K^vii	138.03 (13)
Oⁱⁱⁱ—K—N3^viii	104.76 (11)	K^v—O—H1	102.6
N4^vi—K—N3^viii	76.83 (10)	K^vii—O—H1	102.6
N1—K—N3^viii	70.24 (11)	K^v—O—H2	102.6
N3^vii—K—N3^viii	113.15 (8)	K^vii—O—H2	102.6
O^vi—K—N1^ix	98.92 (11)	H1—O—H2	105.0
Oⁱⁱⁱ—K—N1^ix	169.76 (10)

Symmetry codes: (i) x+1/2, −y+1/2, −z+1; (ii) x+1, y, z; (iii) −x+1, y+1/2, −z+1/2; (iv) −x+3/2, −y+1, z−1/2; (v) −x+1/2, −y+1, z−1/2; (vi) −x+1/2, −y+1, z+1/2; (vii) −x+1, y−1/2, −z+1/2; (viii) −x+3/2, −y+1, z+1/2; (ix) x−1/2, −y+1/2, −z+1; (x) x−1, y, z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O—H2···N1^iv	0.84	2.32	3.157 (5)	178
O—H1···N2^xi	0.84	2.27	2.952 (5)	139

Symmetry codes: (iv) −x+3/2, −y+1, z−1/2; (xi) −x+2, y−1/2, −z+1/2.

Funding information

Funding for this research was provided by: Ministry of Education, Culture, Sports, Science and Technology, MEXT-Supported Program for the Strategic Research Foundation at Private Universities (award No. S1311027).

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