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metal-organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 61| Part 10| October 2005| Pages m2023-m2025
doi:10.1107/S1600536805028825

Guanidinium di­hydrogenarsenate

CROSSMARK_Color_square_no_text.svg
Hazel S. Wilkinsona and William T. A. Harrisona*

aDepartment of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, Scotland
*Correspondence e-mail: w.harrison@abdn.ac.uk

(Received 8 September 2005; accepted 12 September 2005; online 17 September 2005)

The title compound, (CH6N3)[H2AsO4], contains a network of guanidinium cations and dihydrogenarsenate anions. The component species inter­act by way of cation-to-anion N—H⋯O and anion-to-anion O—H⋯O hydrogen bonds, the latter leading to infinite sheets of [H2AsO4]− anions.

Comment

The title compound, (I)[link], was prepared as part of ongoing studies of hydrogen-bonding inter­actions in mol­ecular salts (Wilkinson & Harrison, 2004[Wilkinson, H. S. & Harrison, W. T. A. (2004). Acta Cryst. E60, m1359-m1361.]).

[Scheme 1]

The [H2AsO4]− anion in (I)[link] shows its normal tetra­hedral geometry (Fig. 1[link]) about As [mean As—O = 1.684 (2) Å], with the usual distinction between protonated and unprotonated As—O bond lengths (Wilkinson & Harrison, 2004[Wilkinson, H. S. & Harrison, W. T. A. (2004). Acta Cryst. E60, m1359-m1361.]); see Table 1[link]. The three C—N bond lengths in the propeller-shaped (CH6N3)+ cation are similar (Table 1[link]), indicating that the usual model of electron delocalization in this species, leading to a C—N bond order of 1.33, is applicable here.

As well as Coulombic forces, the component species in (I)[link] inter­act by means of a network of cation-to-anion N—H⋯O and anion-to-anion O—H⋯O hydrogen bonds, as detailed in Table 2[link]. All the guanidinium atoms participate in hydrogen bonds (one of which, via H8, is bifurcated with notably longer H⋯O separations than the others), such that the (CH6N3)+ cation makes N—H⋯O links to five adjacent [H2AsO4]− tetra­hedra as shown in Fig. 2[link]. For the simple N—H⋯O bonds, the mean H⋯O distance = 2.18 Å, mean N⋯O = 2.951 (3) Å, and the mean N—H⋯O angle is 150°.

The [H2AsO4]− units are linked into infinite sheets (Fig. 3[link]) by way of the O—H⋯O hydrogen bonds. The O3—H1⋯O1i inter­action (see Table 2[link] for symmetry codes) results in inversion-symmetry-generated dimeric pairs of [H2AsO4]− tetra­hedra linked by a double (i.e. O—H⋯O + O⋯H—O) hydrogen bond. The O4—H2⋯O2ii bond links the dimers into an infinite sheet (Fig. 3[link]) propagating in (100). The As⋯Asi and As⋯Asii separations are 4.0148 (3) and 5.0190 (3) Å, respectively. If the topological connectivity of the As atoms is considered, a 63 sheet (O′Keeffe & Hyde, 1996[O'Keeffe, M. & Hyde, B. G. (1996). Crystal Structures, 1. Patterns and Symmetry, p 357. Washington DC, USA: Mineralogical Society of America.]) arises, i.e. every As node participates in three polyhedral six-ring loops.

The packing for (I)[link] (Fig. 4[link]) results in alternating organic and inorganic layers with respect to the a axis direction. The structure of (I)[link] is distinct from other ammonium hydrogenarsenate salts where isolated pairs of tetra­hedra (Todd & Harrison, 2005[Todd, M. J. & Harrison, W. T. A. (2005). Acta Cryst. E61, m2026-mm2028.]) or various kinds of polymeric chains (Wilkinson & Harrison, 2004[Wilkinson, H. S. & Harrison, W. T. A. (2004). Acta Cryst. E60, m1359-m1361.]) occur.

[Figure 1]
Figure 1
Asymmetric unit of (I)[link] (50% displacement ellipsoids). The hydrogen bond is indicated by a dashed line.
[Figure 2]
Figure 2
Detail of the cation-to-anion N—H⋯O links (dashed lines) in (I)[link]. Symmetry codes are as in Table 2[link].
[Figure 3]
Figure 3
Detail of a part of a (100) hydrogen-bonded sheet of [H2AsO4]− groups in (I)[link], in polyhedral representation. Symmetry codes are as in Table 2[link].
[Figure 4]
Figure 4
The packing in (I)[link], projected down [001], showing the (100) dihydrogenarsenate layers mediated by guanidinium cations. The N—H⋯O hydrogen bonds are not shown.

Experimental

An aqueous guanidine solution (0.5 M, 10 ml) was added to an H3AsO4 solution (0.5 M, 10 ml) to give a clear solution. A mass of chunks and blocks of (I)[link] grew as the water evaporated over the course of a few days.

Crystal data

  • (CH6N3)[H2AsO4]

  • Mr = 201.02

  • Monoclinic, P 21 /c

  • a = 6.1571 (3) Å

  • b = 13.7052 (6) Å

  • c = 7.7208 (3) Å

  • β = 91.715 (1)°

  • V = 651.22 (5) Å3

  • Z = 4

  • Dx = 2.050 Mg m−3

  • Mo Kα radiation

  • Cell parameters from 4819 reflections

  • θ = 3.0–32.5°

  • μ = 5.18 mm−1

  • T = 295 (2) K

  • Block, colourless

  • 0.49 × 0.29 × 0.13 mm
Data collection

  • Bruker SMART1000 CCD diffractometer

  • ω scans

  • Absorption correction: multi-scan(SADABS; Bruker, 1999[Bruker (1999). SMART (Version 5.624), SAINT (Version 6.02A) and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.])Tmin = 0.172, Tmax = 0.510

  • 7302 measured reflections

  • 2353 independent reflections

  • 2068 reflections with I > 2σ(I)

  • Rint = 0.027

  • θmax = 32.5°

  • h = −9 → 9

  • k = −18 → 20

  • l = −11 → 11
Refinement

  • Refinement on F2

  • R[F2 > 2σ(F2)] = 0.021

  • wR(F2) = 0.058

  • S = 1.06

  • 2353 reflections

  • 83 parameters

  • H-atom parameters constrained

  • w = 1/[σ2(Fo2) + (0.0338P)2 + 0.0391P] where P = (Fo2 + 2Fc2)/3

  • (Δ/σ)max <0.001

  • Δρmax = 0.48 e Å−3

  • Δρmin = −0.62 e Å−3

  • Extinction correction: SHELXL

  • Extinction coefficient: 0.0145 (12)

Table 1
Selected bond lengths (Å)[link]

As1—O1 1.6532 (11)
As1—O2 1.6538 (10)
As1—O4 1.7135 (10)
As1—O3 1.7144 (11)
C1—N1 1.314 (2)
C1—N2 1.323 (2)
C1—N3 1.324 (2)

Table 2
Hydrogen-bond geometry (Å, °)[link]

D—H⋯A D—H H⋯A D⋯A D—H⋯A
O3—H1⋯O1i 0.85 1.83 2.6684 (16) 167
O4—H2⋯O2ii 0.92 1.65 2.5648 (16) 174
N1—H3⋯O2 0.86 2.13 2.9185 (18) 153
N1—H4⋯O1iii 0.86 2.24 2.993 (2) 147
N2—H5⋯O2iv 0.86 2.15 2.955 (2) 157
N2—H6⋯O4v 0.86 2.28 2.994 (2) 140
N3—H7⋯O1iii 0.86 2.11 2.8962 (17) 152
N3—H8⋯O1vi 0.86 2.47 3.1582 (18) 138
N3—H8⋯O4v 0.86 2.55 3.1965 (18) 133
Symmetry codes: (i) -x, -y+1, -z; (ii) [x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]; (iii) x+1, y, z; (iv) [x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]; (v) x+1, y, z+1; (vi) -x+1, -y+1, -z+1.

The O-bound H atoms were found in difference maps and allowed for as riding in their as-found relative positions with Uiso(H) = 1.2Ueq(O). The N-bound H atoms were included in the riding model approximation, with N—H = 0.86 Å and with Uiso(H) = 1.2Ueq(N).

Data collection: SMART (Bruker, 1999[Bruker (1999). SMART (Version 5.624), SAINT (Version 6.02A) and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 1999[Bruker (1999). SMART (Version 5.624), SAINT (Version 6.02A) and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); molecular graphics: ORTEP3 (Farrugia, 1997[Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.]) & ATOMS (Shape Software, 2004[Shape Software (2004). ATOMS. 525 Hidden Valley Road, Kingsport, Tennessee, USA.]); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536805028825/tk6259sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536805028825/tk6259Isup2.hkl


Comment top

The title compound, (I), was prepared as part of on-going studies of hydrogen-bonding interactions in molecular salts (Wilkinson & Harrison, 2004).

The [H2AsO4]− moiety in (I) shows its normal tetrahedral geometry, Fig. 1, about As [mean As—O = 1.684 (2) Å], with the usual distinction between protonated and un-protonated As—O bond lengths (Wilkinson & Harrison, 2004); see Table 1. The three C—N bond lengths in the propeller-shaped [CH6N3]+ entity are similar (Table 1), indicating that the usual model of electron delocalization in this species leading to a C—N bond order of 1.33 is applicable here.

As well as Coulombic forces, the component species in (I) interact by means of a network of cation-to-anion N—H···O and anion-to-anion O—H···O H-bonds, as detailed in Table 2. A l l the guanidinium-H atoms participate in hydrogen bonds (one of which, via H8, is bifurcated with notably longer H···O separations than the others), such that the [CH6N3]+ moiety makes N—H···O links to five adjacent [H2AsO4]− tetrahedra as shown in Fig. 2. For the simple N—H···O bonds, the mean H···O distance = 2.18 Å, mean N···O = 2.951 (3) Å, and the mean N—H···O angle is 150°.

The [H2AsO4]− units are linked into infinte sheets (Fig. 3) by way of the O—H···O hydrogen bonds. The O3—H1···O1i interaction (see Table 2 for symmetry codes) results in inversion-symmetry-generated dimeric pairs of [H2AsO4]− tetrahedra linked by a double (i.e. O—H···O + O···H—O) hydrogen bond. The O4—H2···O2ii bond links the dimers into an infinte sheet (Fig. 3) propagating in (100). The As···Asi and As···Asii separations are 4.0148 (3) and 5.0190 (3) Å, respectively. If the topological connectivity of the As atoms is considered, a 63 sheet (O'Keeffe & Hyde, 1996) arises, i.e. every As node participates in three polyhedral six-ring loops.

The unit-cell packing for (I) (Fig. 4) results in alternating organic and inorganic layers with respect to the a axis direction. The structure of (I) is distinct from other ammonium hydrogenarsenate salts where isolated pairs of tetrahedra (Todd & Harrison, 2005) or various kinds of polymeric chains (Wilkinson & Harrison, 2004) occur.

Experimental top

An aqueous guanidine solution (0.5 M, 10 ml) was added to an H3AsO4 solution (0.5 M, 10 ml) to give a clear solution. A mass of chunks and blocks of (I) grew as the water evaporated over the course of a few days.

Refinement top

The O-bound H atoms were found in difference maps and fixed in these positions with Uiso(H) = 1.2Ueq(O). The N-bound H atoms were included in the riding model approximation, with N—H = 0.86 Å and with Uiso(H) = 1.2Ueq(N).

Computing details top

Data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997) & ATOMS (Shape Software, 2004); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. Asymmetric unit of (I) (50% displacement ellipsoids). The hydrogen bond is indicated by a dashed line.
[Figure 2] Fig. 2. Detail of the cation-to-anion N—H···O links (dashed lines) in (I). Symmetry codes are as in Table 2.
[Figure 3] Fig. 3. Detail of a part of a (100) hydrogen-bonded sheet of [H2AsO4]− groups in (I), in polyhedral representation. Symmetry codes are as in Table 2.
[Figure 4] Fig. 4. Unit-cell packing in (I), projected down [001], showing the (100) dihydrogenarsenate layers mediated by guanidinium cations. The N—H···O hydrogen bonds are not shown.
(I) top
Crystal data top
(CH6N3)[H2AsO4]F(000) = 400
Mr = 201.02Dx = 2.050 Mg m−3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 4819 reflections
a = 6.1571 (3) Åθ = 3.0–32.5°
b = 13.7052 (6) ŵ = 5.18 mm−1
c = 7.7208 (3) ÅT = 295 K
β = 91.715 (1)°Block, colourless
V = 651.22 (5) Å30.49 × 0.29 × 0.13 mm
Z = 4
Data collection top
Bruker SMART1000 CCD
diffractometer		2353 independent reflections
Radiation source: fine-focus sealed tube2068 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.027
ω scansθmax = 32.5°, θmin = 3.0°
Absorption correction: multi-scan
(SADABS; Bruker, 1999)		h = −9→9
Tmin = 0.172, Tmax = 0.510k = −18→20
7302 measured reflectionsl = −11→11
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.021H-atom parameters constrained
wR(F2) = 0.058 w = 1/[σ2(Fo2) + (0.0338P)2 + 0.0391P]
where P = (Fo2 + 2Fc2)/3
S = 1.06(Δ/σ)max < 0.001
2353 reflectionsΔρmax = 0.48 e Å−3
83 parametersΔρmin = −0.62 e Å−3
0 restraintsExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0145 (12)
Crystal data top
(CH6N3)[H2AsO4]V = 651.22 (5) Å3
Mr = 201.02Z = 4
Monoclinic, P21/cMo Kα radiation
a = 6.1571 (3) ŵ = 5.18 mm−1
b = 13.7052 (6) ÅT = 295 K
c = 7.7208 (3) Å0.49 × 0.29 × 0.13 mm
β = 91.715 (1)°
Data collection top
Bruker SMART1000 CCD
diffractometer		2353 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 1999)		2068 reflections with I > 2σ(I)
Tmin = 0.172, Tmax = 0.510Rint = 0.027
7302 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0210 restraints
wR(F2) = 0.058H-atom parameters constrained
S = 1.06Δρmax = 0.48 e Å−3
2353 reflectionsΔρmin = −0.62 e Å−3
83 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.

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
As10.04340 (2)0.367017 (10)0.104376 (16)0.02035 (6)
O1−0.10944 (19)0.45045 (8)0.19597 (13)0.0295 (2)
O20.13284 (18)0.27840 (8)0.23321 (14)0.0304 (2)
O30.27494 (18)0.41686 (9)0.02378 (15)0.0343 (3)
H10.24060.4633−0.04440.041*
O4−0.10648 (19)0.32367 (9)−0.06967 (14)0.0324 (2)
H2−0.02880.2840−0.14190.039*
C10.6107 (3)0.37973 (10)0.5461 (2)0.0256 (3)
N10.5194 (3)0.36882 (10)0.39137 (19)0.0347 (3)
H30.39300.34240.38030.042*
H40.58600.38810.30120.042*
N20.5110 (3)0.35063 (13)0.6865 (2)0.0418 (4)
H50.38460.32410.67720.050*
H60.57270.35820.78700.050*
N30.8045 (2)0.42143 (11)0.55908 (18)0.0337 (3)
H70.86780.44070.46740.040*
H80.86700.42920.65920.040*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
As10.02193 (8)0.02172 (9)0.01733 (8)0.00041 (5)−0.00081 (5)0.00190 (4)
O10.0377 (6)0.0279 (5)0.0232 (5)0.0053 (5)0.0067 (4)−0.0013 (4)
O20.0293 (5)0.0311 (6)0.0305 (5)0.0011 (4)−0.0031 (4)0.0125 (4)
O30.0268 (5)0.0405 (7)0.0358 (6)−0.0019 (5)0.0041 (4)0.0125 (5)
O40.0304 (5)0.0377 (7)0.0287 (5)0.0057 (5)−0.0080 (4)−0.0100 (5)
C10.0269 (7)0.0251 (7)0.0247 (6)0.0004 (5)0.0002 (5)0.0008 (5)
N10.0322 (7)0.0448 (9)0.0269 (7)−0.0067 (6)−0.0055 (5)0.0017 (5)
N20.0361 (8)0.0623 (10)0.0272 (7)−0.0125 (7)0.0018 (6)0.0078 (7)
N30.0327 (7)0.0415 (8)0.0266 (6)−0.0126 (6)−0.0011 (5)−0.0010 (5)
Geometric parameters (Å, º) top
As1—O11.6532 (11)C1—N31.324 (2)
As1—O21.6538 (10)N1—H30.8600
As1—O41.7135 (10)N1—H40.8600
As1—O31.7144 (11)N2—H50.8600
O3—H10.8491N2—H60.8600
O4—H20.9226N3—H70.8600
C1—N11.314 (2)N3—H80.8600
C1—N21.323 (2)
O1—As1—O2115.74 (6)N2—C1—N3120.48 (16)
O1—As1—O4105.97 (6)C1—N1—H3120.0
O2—As1—O4112.26 (6)C1—N1—H4120.0
O1—As1—O3111.71 (6)H3—N1—H4120.0
O2—As1—O3104.21 (6)C1—N2—H5120.0
O4—As1—O3106.72 (6)C1—N2—H6120.0
As1—O3—H1109.2H5—N2—H6120.0
As1—O4—H2113.7C1—N3—H7120.0
N1—C1—N2120.96 (16)C1—N3—H8120.0
N1—C1—N3118.57 (15)H7—N3—H8120.0
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O3—H1···O1i0.851.832.6684 (16)167
O4—H2···O2ii0.921.652.5648 (16)174
N1—H3···O20.862.132.9185 (18)153
N1—H4···O1iii0.862.242.993 (2)147
N2—H5···O2iv0.862.152.955 (2)157
N2—H6···O4v0.862.282.994 (2)140
N3—H7···O1iii0.862.112.8962 (17)152
N3—H8···O1vi0.862.473.1582 (18)138
N3—H8···O4v0.862.553.1965 (18)133
Symmetry codes: (i) −x, −y+1, −z; (ii) x, −y+1/2, z−1/2; (iii) x+1, y, z; (iv) x, −y+1/2, z+1/2; (v) x+1, y, z+1; (vi) −x+1, −y+1, −z+1.

Experimental details

Crystal data
Chemical formula(CH6N3)[H2AsO4]
Mr201.02
Crystal system, space groupMonoclinic, P21/c
Temperature (K)295
a, b, c (Å)6.1571 (3), 13.7052 (6), 7.7208 (3)
β (°) 91.715 (1)
V (Å3)651.22 (5)
Z4
Radiation typeMo Kα
µ (mm−1)5.18
Crystal size (mm)0.49 × 0.29 × 0.13
Data collection
DiffractometerBruker SMART1000 CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 1999)
Tmin, Tmax0.172, 0.510
No. of measured, independent and
observed [I > 2σ(I)] reflections		7302, 2353, 2068
Rint0.027
(sin θ/λ)max (Å−1)0.756
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.021, 0.058, 1.06
No. of reflections2353
No. of parameters83
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å−3)0.48, −0.62

Computer programs: SMART (Bruker, 1999), SAINT (Bruker, 1999), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 (Farrugia, 1997) & ATOMS (Shape Software, 2004), SHELXL97.

Selected bond lengths (Å) top
As1—O11.6532 (11)C1—N11.314 (2)
As1—O21.6538 (10)C1—N21.323 (2)
As1—O41.7135 (10)C1—N31.324 (2)
As1—O31.7144 (11)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O3—H1···O1i0.851.832.6684 (16)167
O4—H2···O2ii0.921.652.5648 (16)174
N1—H3···O20.862.132.9185 (18)153
N1—H4···O1iii0.862.242.993 (2)147
N2—H5···O2iv0.862.152.955 (2)157
N2—H6···O4v0.862.282.994 (2)140
N3—H7···O1iii0.862.112.8962 (17)152
N3—H8···O1vi0.862.473.1582 (18)138
N3—H8···O4v0.862.553.1965 (18)133
Symmetry codes: (i) −x, −y+1, −z; (ii) x, −y+1/2, z−1/2; (iii) x+1, y, z; (iv) x, −y+1/2, z+1/2; (v) x+1, y, z+1; (vi) −x+1, −y+1, −z+1.
 

Acknowledgements

HSW thanks the Carnegie Trust for the Universities of Scotland for an undergraduate vacation studentship.

References

First citationBruker (1999). SMART (Version 5.624), SAINT (Version 6.02A) and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
 First citationFarrugia, L. J. (1997). J. Appl. Cryst. 30, 565.  CrossRef IUCr Journals Google Scholar
 First citationO'Keeffe, M. & Hyde, B. G. (1996). Crystal Structures, 1. Patterns and Symmetry, p 357. Washington DC, USA: Mineralogical Society of America.  Google Scholar
 First citationShape Software (2004). ATOMS. 525 Hidden Valley Road, Kingsport, Tennessee, USA.  Google Scholar
 First citationSheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.  Google Scholar
 First citationTodd, M. J. & Harrison, W. T. A. (2005). Acta Cryst. E61, m2026–mm2028.  Web of Science CSD CrossRef IUCr Journals Google Scholar
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Journal logoCRYSTALLOGRAPHIC
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ISSN: 2056-9890
Volume 61| Part 10| October 2005| Pages m2023-m2025
doi:10.1107/S1600536805028825
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