Crystal structure of metronidazolium tetra­chlorido­aurate(III)

Quinlivan, P.J.; Wu, J.-S.; Upmacis, R.K.

doi:10.1107/S2056989015010798

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ISSN: 2056-9890

Volume 71| Part 7| July 2015| Pages 810-812

doi:10.1107/S2056989015010798

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Crystal structure of metronidazolium tetrachloridoaurate(III)

Patrick J. Quinlivan,^a Ja-Shin Wu ^b and Rita K. Upmacis ^b ^*

^aDepartment of Chemistry, Columbia University, New York, NY 10027, USA, and ^bHaskins Laboratories, Dept. of Chemistry, Pace University, New York, NY 10038, USA
^*Correspondence e-mail: rupmacis@pace.edu

Edited by A. J. Lough, University of Toronto, Canada (Received 14 May 2015; accepted 4 June 2015; online 17 June 2015)

Metronidazole (MET) [systematic names: 1-(2-hydroxyethyl)-2-methyl-5-nitro-1H-imidazole and 2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethanol] is a medication that is used to treat infections from a variety of anaerobic organisms. As with other imidazole derivatives, metronidazole is also susceptible to protonation. However, there are few reports of the structures of metronidazolium derivatives. In the title compound, (C₆H₁₀N₃O₃)[AuCl₄] [systematic name: 1-(2-hydroxyethyl)-2-methyl-5-nitro-1H-imidazol-3-ium tetrachloridoaurate(III)], the asymmetric unit consists of a metronidazolium cation, [H(MET)]⁺, and a tetrachloridoaurate(III) anion, [AuCl₄]⁻, in which the Au^III ion is in a slightly distorted square-planar coordination environment. In the cation, the nitro group is essentially coplanar with the imidazole ring, as indicated by an O N—C=C torsion angle of −0.2 (4)°, while the hydroxyethyl group is in a coiled conformation, with an O(H)—C—C—N torsion angle of 62.3 (3)°. In the crystal, the anion and cation are linked by an intermolecular O—H⋯Cl hydrogen bond. In addition, the N—H group of the metronidazolium ion serves as a hydrogen-bond donor to the O atom of the hydroxyethyl group of a symmetry-related molecule, leading to the formation of chains along [010].

Keywords: crystal structure; gold; metronidazole; flagyl; tetrachloridoaurate(III); O—H⋯Cl hydrogen bonding.

CCDC reference: 1404845

1. Chemical context

Metronidazole (MET), marketed as flagyl, and also known by the systematic names 1-(2-hydroxyethyl)-2-methyl-5-nitro-1H-imidazole and 2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethanol, is a medication that has been used for the treatment of parasitic infections, such as trichomoniasis, amoebiasis and giardiasis, and is also effective against anaerobic bacteria (Freeman et al., 1997 ; Miljkovic et al., 2014 ; Soares et al., 2012 ; Samuelson, 1999 ; Lofmark et al., 2010 ; Contreras et al., 2009 ). Metronidazole possesses a variety of functional groups, and the two-coordinate nitrogen atom of the imidazole ring has been shown to be an effective ligand for a variety of metals (Contreras et al., 2009). This nitrogen atom is also susceptible to protonation, but there are few structures of metronidazolium derivatives reported in the literature (Yang, 2008 ; Wang et al., 2010 ). We describe herein the structure of metronidazolium tetrachloridoaurate(III), which is obtained by the addition of MET to HAuCl₄.

2. Structural commentary

The asymmetric unit of [H(MET)][AuCl₄] consists of a metronidazolium cation, [H(MET)]⁺, hydrogen-bonded to a square-planar tetrachloridoaurate(III) anion, [AuCl₄]⁻, by an O—H⋯Cl hydrogen bond as illustrated in Fig. 1. The O3⋯Cl3 distance of 3.169 (2) Å is comparable to the values in other tetrachloridoaurate(III) derivatives that exhibit O—H⋯Cl hydrogen bonds. As an illustration, bis{2-[(2-hydroxyethyl)iminomethyl]phenolato}gold(III) tetrachloridoaurate(III) possesses an O—H⋯Cl hydrogen bond between a hydroxyethyl group and [AuCl₄]⁻, with an O(H)⋯Cl distance of 3.365 Å (Nockemann et al., 2007 ). For further reference, the average O⋯Cl distance in compounds that have O—H⋯Cl interactions is 3.196 (3) Å (Steiner, 2002 ). The nitro group is almost coplanar with the imidazole ring, as indicated by an O1—N3—C2—C1 torsion angle of −0.2 (4)°, while the hydroxyethyl group exhibits an O3—C6—C5—N2 torsion angle of 62.3 (3)°, describing a coiled conformation.

Figure 1
The asymmetric unit of the title compound, shown with 20% probability displacement ellipsoids. The O3—H3⋯Cl3 hydrogen bond is shown as an open bond.

3. Supramolecular features

In the crystal, the N—H group of the metronidazolium ion serves as a hydrogen-bond donor to the oxygen atom of the hydroxyethyl group of a symmetry-related molecule, forming a chain along [010] in which each O—H group is O—H⋯Cl hydrogen bonded to a [AuCl₄]⁻ ion (Table 1 and Fig. 2). The N⋯O distance of 2.729 (3) Å associated with the hydrogen bond is comparable to that observed for metronidazole [2.816 (2) Å] (Blaton et al., 1979 ; Galván-Tejada et al., 2002 ). However, an important difference between the hydrogen bonds in metronidazole and metronidazolium is that the alcohol O—H group is the hydrogen-bond donor for metronidazole (i.e. O—H⋯N), while the N—H group is the hydrogen-bond donor for metronidazolium (i.e. N—H⋯O).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H01⋯O3ⁱ	0.94 (4)	1.81 (4)	2.729 (3)	166 (3)
O3—H3⋯Cl3	0.67 (4)	2.54 (4)	3.169 (2)	158 (4)
Symmetry code: (i) $[-x+{\script{3\over 2}}, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ .

Figure 2
Part of the crystal structure showing a hydrogen-bonded chain (open bonds) along [010].

4. Database survey

Metronidazolium derivatives that feature other counter-ions, e.g. 3-carboxy-4-hydroxybenzenesulfonate and perchlorate have been reported (Yang, 2008; Wang et al., 2010), as have a variety of tetrachloridoaurate(III) complexes (Johnson & Steed, 1998 ; Pluzhnik-Gladyr et al., 2014 ; Fazaeli et al., 2010 ).

5. Synthesis and crystallization

Crystals of composition [H(MET)][AuCl₄] were obtained by combining HAuCl₄·H₂O (0.12 mmol) with MET (0.20 mmol) in MeOH (2 ml), followed by evaporation of MeOH, and crystallization from Et₂O.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms bonded to C atoms were refined with a riding model, with C—H = 0.95–0.99 Å and U_iso(H) = 1.2U_eq(C) or 1.5U_eq(C_methyl). H atoms bonded to N and O atoms were refined independently with isotropic displacement parameters.

Table 2
Experimental details

Crystal data
Chemical formula	(C₆H₁₀N₃O₃)[AuCl₄]
M_r	510.94
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	130
a, b, c (Å)	7.324 (2), 11.972 (4), 15.667 (5)
β (°)	94.384 (4)
V (Å³)	1369.6 (8)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	11.52
Crystal size (mm)	0.23 × 0.04 × 0.02

Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2013 )
T_min, T_max	0.426, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	22024, 4214, 3673
R_int	0.041
(sin θ/λ)_max (Å⁻¹)	0.718

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.021, 0.045, 1.16
No. of reflections	4214
No. of parameters	163
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	1.30, −1.22
Computer programs: APEX2 and, SAINT (Bruker, 2013), SHELXS97 and SHELXTL (Sheldrick, 2008 ), SHELXL2014 (Sheldrick, 2015 ).

Supporting information

CCDC reference: 1404845

Crystal structure: contains datablock I. DOI: 10.1107/S2056989015010798/lh5766sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S2056989015010798/lh5766Isup3.hkl

checkCIF report

Chemical context top

Metronidazole (MET), marketed as flagyl, and also known by the systematic names 1-(2-hydroxyethyl)-2-methyl-5-nitro-1H-imidazole and 2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethanol, is a medication that has been used for the treatment of parasitic infections, such as trichomoniasis, amoebiasis and giardiasis, and is also effective against anaerobic bacteria (Freeman et al., 1997; Miljkovic et al., 2014; Soares et al., 2012; Samuelson, 1999; Lofmark et al., 2010; Contreras et al., 2009). Metronidazole possesses a variety of functional groups, and the two-coordinate nitrogen atom of the imidazole ring has been shown to be an effective ligand for a variety of metals (Contreras et al., 2009). This nitrogen atom is also susceptible to protonation, but there are few structures of metronidazolium derivatives reported in the literature (Yang, 2008; Wang et al., 2010). We describe herein the structure of metronidazolium tetrachloridoaurate(III), which is obtained by the addition of MET to HAuCl₄.

Structural commentary top

The asymmetric unit of [H(MET)][AuCl₄] consists of a metronidazolium cation, [H(MET)]⁺ hydrogen bonded to a square-planar tetrachloridoaurate(III) anion, [AuCl₄]^–, by an O—H···Cl hydrogen bond as illustrated in Fig. 1. The O3···Cl3 distance of 3.169 (2) Å is comparable to the values in other tetrachloridoaurate(III) derivatives that exhibit O—H···Cl hydrogen bonds. As an illustration, bis{2-[(2-hydroxyethyl)iminomethyl]phenolato}gold(III) tetrachloridoaurate(III) possesses an O–H···Cl hydrogen bond between a hydroxyethyl group and [AuCl₄]^–, with an O(H)···Cl distance of 3.365 Å (Nockemann et al., 2007). For further reference, the average O···Cl distance in compounds that have O—H···Cl interactions is 3.196 (3) Å (Steiner, 2002). The nitro group is almost coplanar with the imidazole ring, as indicated by an O1—N3—C2—C1 torsion angle of -0.2 (4)°, while the hydroxyethyl group exhibits an O3—C6—C5—N2 torsion angle of 62.3 (3)°, describing a coiled conformation.

Supramolecular features top

In the crystal, the N—H group of the metronidazolium ion serves as a hydrogen-bond donor to the oxygen atom of the hydroxyethyl group of a symmetry-related molecule, forming a chain along [010] in which each O—H group is O—H···Cl hydrogen bonded to a [AuCl₄]^– ion (Table 1 and Fig. 2). The N···O distance of 2.729 (3) Å associated with the hydrogen bond is comparable to that observed for metronidazole [2.816 (2) Å] (Blaton et al., 1979, Galván-Tejada et al., 2002). However, an important difference between the hydrogen bonds in metronidazole and metronidazolium is that the alcohol O—H group is the hydrogen-bond donor for metronidazole (i.e. O—H···N), while the N—H group is the hydrogen-bond donor for metronidazolium (i.e. N—H···O).

Database survey top

Metronidazolium derivatives that feature other counter-ions, e.g. 3-carboxy-4-hydroxybenzenesulfonate and perchlorate have been reported (Yang, 2008; Wang et al., 2010), as have a variety of tetrachloridoaurate(III) complexes (Johnson & Steed, 1998; Pluzhnik-Gladyr et al., 2014; Fazaeli et al., 2010).

Synthesis and crystallization top

Crystals of composition [H(MET)][AuCl₄] were obtained by combining HAuCl₄.H₂O (0.12 mmol) with MET (0.20 mmol) in MeOH (2 ml), followed by evaporation of MeOH, and crystallization from Et₂O.

Refinement top

Related literature top

For related literature, see: Blaton et al. (1979); Contreras et al. (2009); Fazaeli et al. (2010); Freeman et al. (1997); Galván-Tejada, Bernes, Castillo-Blum, Noth, Vicente & Barba-Behrens (2002); Johnson & Steed (1998); Lofmark et al. (2010); Miljkovic et al. (2014); Nockemann et al. (2007); Pluzhnik-Gladyr, Kravtsov, Fonari & Kamalov (2014); Samuelson (1999); Sheldrick (2008); Sheldrick (2015); Soares et al. (2012); Steiner (2002); Wang et al. (2010); Yang (2008).

Computing details top

Data collection: APEX2 (Bruker, 2013); cell refinement: SAINT (Bruker, 2013); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

	Fig. 1. The asymmetric unit of the title compound, shown with 20% probability displacement ellipsoids. The O3—H3···Cl3 hydrogen bond is shown as an open bond.
	Fig. 2. Part of the crystal structure showing a hydrogen-bonded chain (open bonds) along [010].

1-(2-Hydroxyethyl)-2-methyl-5-nitro-1H-imidazol-3-ium tetrachloridoaurate(III)] top

Crystal data top

(C₆H₁₀N₃O₃)[AuCl₄]	F(000) = 952
M_r = 510.94	D_x = 2.478 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
a = 7.324 (2) Å	Cell parameters from 9874 reflections
b = 11.972 (4) Å	θ = 2.6–30.6°
c = 15.667 (5) Å	µ = 11.52 mm⁻¹
β = 94.384 (4)°	T = 130 K
V = 1369.6 (8) Å³	Plate, yellow
Z = 4	0.23 × 0.04 × 0.02 mm

Data collection top

Bruker APEXII CCD diffractometer	3673 reflections with I > 2σ(I)
ϕ and ω scans	R_int = 0.041
Absorption correction: multi-scan (SADABS; Bruker, 2013)	θ_max = 30.7°, θ_min = 2.1°
T_min = 0.426, T_max = 0.746	h = −10→10
22024 measured reflections	k = −17→17
4214 independent reflections	l = −22→22

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.021	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.045	w = 1/[σ²(F_o²) + (0.0129P)²] where P = (F_o² + 2F_c²)/3
S = 1.16	(Δ/σ)_max = 0.001
4214 reflections	Δρ_max = 1.30 e Å⁻³
163 parameters	Δρ_min = −1.22 e Å⁻³

Crystal data top

(C₆H₁₀N₃O₃)[AuCl₄]	V = 1369.6 (8) Å³
M_r = 510.94	Z = 4
Monoclinic, P2₁/n	Mo Kα radiation
a = 7.324 (2) Å	µ = 11.52 mm⁻¹
b = 11.972 (4) Å	T = 130 K
c = 15.667 (5) Å	0.23 × 0.04 × 0.02 mm
β = 94.384 (4)°

Data collection top

Bruker APEXII CCD diffractometer	4214 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2013)	3673 reflections with I > 2σ(I)
T_min = 0.426, T_max = 0.746	R_int = 0.041
22024 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.021	0 restraints
wR(F²) = 0.045	H atoms treated by a mixture of independent and constrained refinement
S = 1.16	Δρ_max = 1.30 e Å⁻³
4214 reflections	Δρ_min = −1.22 e Å⁻³
163 parameters

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.

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

	x	y	z	U_iso*/U_eq
Au	0.36629 (2)	0.79983 (2)	0.58625 (2)	0.01868 (4)
Cl1	0.26070 (11)	0.84595 (7)	0.45047 (5)	0.03247 (17)
Cl2	0.44092 (10)	0.62541 (6)	0.54111 (5)	0.03012 (16)
Cl3	0.46029 (10)	0.75210 (6)	0.72389 (5)	0.02610 (15)
Cl4	0.29498 (10)	0.97418 (6)	0.63205 (5)	0.02831 (15)
O1	0.8047 (3)	0.7553 (2)	0.41611 (14)	0.0367 (5)
O2	0.9242 (3)	0.60835 (18)	0.47815 (14)	0.0331 (5)
O3	0.7450 (3)	0.55236 (18)	0.73360 (15)	0.0265 (5)
H3	0.684 (5)	0.591 (3)	0.719 (2)	0.042 (13)*
N1	0.8446 (3)	0.89061 (19)	0.65413 (15)	0.0175 (4)
H01	0.810 (5)	0.953 (3)	0.685 (2)	0.042 (10)*
N2	0.9387 (3)	0.72022 (17)	0.63739 (14)	0.0159 (4)
N3	0.8670 (3)	0.70319 (19)	0.47846 (15)	0.0223 (5)
C1	0.8127 (4)	0.8685 (2)	0.56913 (17)	0.0191 (5)
H1A	0.7604	0.9173	0.5261	0.023*
C2	0.8708 (3)	0.7626 (2)	0.55853 (17)	0.0158 (5)
C3	0.9200 (4)	0.8016 (2)	0.69521 (17)	0.0170 (5)
C4	0.9783 (4)	0.7982 (3)	0.78720 (19)	0.0272 (6)
H4A	0.9318	0.8643	0.8154	0.041*
H4B	1.1123	0.7972	0.7949	0.041*
H4C	0.9295	0.7307	0.8126	0.041*
C5	1.0107 (4)	0.6070 (2)	0.65912 (18)	0.0198 (5)
H5A	1.0863	0.6102	0.7142	0.024*
H5B	1.0904	0.5822	0.6145	0.024*
C6	0.8579 (4)	0.5230 (2)	0.66604 (18)	0.0227 (6)
H6A	0.7818	0.5199	0.6111	0.027*
H6B	0.9111	0.4479	0.6773	0.027*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Au	0.01490 (5)	0.01746 (6)	0.02409 (6)	−0.00147 (4)	0.00416 (4)	−0.00253 (4)
Cl1	0.0438 (4)	0.0304 (4)	0.0234 (4)	0.0042 (3)	0.0037 (3)	−0.0009 (3)
Cl2	0.0286 (4)	0.0222 (3)	0.0400 (4)	0.0024 (3)	0.0057 (3)	−0.0092 (3)
Cl3	0.0255 (3)	0.0251 (3)	0.0272 (4)	0.0036 (3)	−0.0008 (3)	−0.0012 (3)
Cl4	0.0360 (4)	0.0193 (3)	0.0292 (4)	0.0033 (3)	0.0002 (3)	−0.0038 (3)
O1	0.0516 (15)	0.0375 (13)	0.0193 (11)	0.0047 (11)	−0.0090 (10)	−0.0008 (10)
O2	0.0468 (14)	0.0221 (11)	0.0309 (12)	0.0056 (10)	0.0058 (10)	−0.0077 (9)
O3	0.0250 (11)	0.0233 (11)	0.0327 (13)	0.0053 (9)	0.0109 (9)	0.0075 (9)
N1	0.0172 (10)	0.0152 (10)	0.0203 (11)	−0.0003 (9)	0.0023 (9)	−0.0003 (9)
N2	0.0146 (10)	0.0157 (10)	0.0175 (11)	0.0000 (8)	0.0021 (8)	0.0014 (8)
N3	0.0253 (12)	0.0233 (12)	0.0181 (12)	−0.0032 (10)	0.0010 (9)	−0.0019 (9)
C1	0.0217 (13)	0.0198 (13)	0.0157 (12)	0.0003 (10)	−0.0001 (10)	0.0012 (10)
C2	0.0184 (12)	0.0152 (11)	0.0138 (12)	−0.0023 (10)	0.0008 (9)	−0.0006 (9)
C3	0.0146 (12)	0.0188 (12)	0.0180 (13)	−0.0012 (10)	0.0038 (10)	0.0002 (10)
C4	0.0292 (16)	0.0355 (17)	0.0167 (14)	0.0031 (13)	0.0011 (12)	−0.0009 (12)
C5	0.0181 (12)	0.0170 (12)	0.0245 (14)	0.0051 (10)	0.0026 (10)	0.0064 (10)
C6	0.0254 (14)	0.0164 (13)	0.0271 (15)	0.0029 (11)	0.0072 (12)	0.0046 (11)

Geometric parameters (Å, º) top

Au—Cl1	2.2752 (10)	N2—C5	1.485 (3)
Au—Cl4	2.2807 (9)	N3—C2	1.441 (3)
Au—Cl2	2.2844 (9)	C1—C2	1.351 (4)
Au—Cl3	2.2855 (10)	C1—H1A	0.9500
O1—N3	1.218 (3)	C3—C4	1.472 (4)
O2—N3	1.210 (3)	C4—H4A	0.9800
O3—C6	1.436 (3)	C4—H4B	0.9800
O3—H3	0.67 (4)	C4—H4C	0.9800
N1—C3	1.341 (3)	C5—C6	1.515 (4)
N1—C1	1.360 (3)	C5—H5A	0.9900
N1—H01	0.94 (4)	C5—H5B	0.9900
N2—C3	1.345 (3)	C6—H6A	0.9900
N2—C2	1.392 (3)	C6—H6B	0.9900

Cl1—Au—Cl4	90.14 (3)	N1—C3—N2	108.2 (2)
Cl1—Au—Cl2	90.27 (3)	N1—C3—C4	124.7 (2)
Cl4—Au—Cl2	179.36 (3)	N2—C3—C4	127.0 (2)
Cl1—Au—Cl3	177.66 (3)	C3—C4—H4A	109.5
Cl4—Au—Cl3	89.52 (3)	C3—C4—H4B	109.5
Cl2—Au—Cl3	90.09 (3)	H4A—C4—H4B	109.5
C6—O3—H3	108 (3)	C3—C4—H4C	109.5
C3—N1—C1	110.4 (2)	H4A—C4—H4C	109.5
C3—N1—H01	120 (2)	H4B—C4—H4C	109.5
C1—N1—H01	129 (2)	N2—C5—C6	111.8 (2)
C3—N2—C2	106.6 (2)	N2—C5—H5A	109.3
C3—N2—C5	124.1 (2)	C6—C5—H5A	109.3
C2—N2—C5	129.3 (2)	N2—C5—H5B	109.3
O2—N3—O1	125.9 (3)	C6—C5—H5B	109.3
O2—N3—C2	118.9 (2)	H5A—C5—H5B	107.9
O1—N3—C2	115.2 (2)	O3—C6—C5	111.1 (2)
C2—C1—N1	105.7 (2)	O3—C6—H6A	109.4
C2—C1—H1A	127.1	C5—C6—H6A	109.4
N1—C1—H1A	127.1	O3—C6—H6B	109.4
C1—C2—N2	109.1 (2)	C5—C6—H6B	109.4
C1—C2—N3	125.8 (2)	H6A—C6—H6B	108.0
N2—C2—N3	125.1 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H01···O3ⁱ	0.94 (4)	1.81 (4)	2.729 (3)	166 (3)
O3—H3···Cl3	0.67 (4)	2.54 (4)	3.169 (2)	158 (4)

Symmetry code: (i) −x+3/2, y+1/2, −z+3/2.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H01···O3ⁱ	0.94 (4)	1.81 (4)	2.729 (3)	166 (3)
O3—H3···Cl3	0.67 (4)	2.54 (4)	3.169 (2)	158 (4)

Symmetry code: (i) −x+3/2, y+1/2, −z+3/2.

Experimental details

Crystal data
Chemical formula	(C₆H₁₀N₃O₃)[AuCl₄]
M_r	510.94
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	130
a, b, c (Å)	7.324 (2), 11.972 (4), 15.667 (5)
β (°)	94.384 (4)
V (Å³)	1369.6 (8)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	11.52
Crystal size (mm)	0.23 × 0.04 × 0.02

Data collection
Diffractometer	Bruker APEXII CCD diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2013)
T_min, T_max	0.426, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	22024, 4214, 3673
R_int	0.041
(sin θ/λ)_max (Å⁻¹)	0.718

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.021, 0.045, 1.16
No. of reflections	4214
No. of parameters	163
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	1.30, −1.22

Computer programs: APEX2 (Bruker, 2013), SAINT (Bruker, 2013), SHELXS97 (Sheldrick, 2008), SHELXL2014 (Sheldrick, 2015), SHELXTL (Sheldrick, 2008).

Acknowledgements

RKU would like to thank Pace University for research support. Gerard Parkin (Columbia University) is thanked for helpful discussions.

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Volume 71| Part 7| July 2015| Pages 810-812

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