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

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ISSN: 2056-9890

5-tert-But­yl-4-nitro-1H-pyrazol-3-ol

aSchool of Science and the Environment, Coventry University, Coventry CV1 5FB, England, and bKey Organics Ltd, Highfield Industrial Estate, Camelford, Cornwall PL32 9QZ, England
*Correspondence e-mail: apx106@coventry.ac.uk

(Received 6 April 2005; accepted 28 June 2005; online 6 July 2005)

The structure of the title compound, C7H11N3O3, consists of mol­ecules that pack in a linear hydrogen-bonded ribbon motif. This hydrogen-bonding arrangement is constructed through two dimer formations, one that is atypical of pyrazoles (N—H⋯N) and the other via an inter­action from the hydr­oxy OH group to one of the nitro O atoms.

Comment

Pyrazoles and related compounds are common mol­ecules used in coordination or organometallic chemistry as bridging ligands, utilizing the ring positions of the two N atoms. There are 1388 structures in the Cambridge Structural Database (CSD; Version 5.26, November 2004; Allen, 2002[Allen, F. H. (2002). Acta Cryst. B58, 380-388.]) that contain a pyrazole ring with the extra search constraints `no extra cyclic routes' and `require 3D coordinates'. This number reduces to 23 for 4-nitro­pyrazoles, 80 for 5-tert-butyl­pyrazoles, and 15 for 3-hydroxy­pyrazoles. Inter­estingly, there is only one structure (CSD refcode: WILBAU), that of 3,5-di-tert-but­yl-4-nitro­pyrazole (Llamas-Saiz et al., 1994[Llamas-Saiz, A. L., Foces-Foces, C., Cano, F. H., Jimenez, P., Laynez, J., Meutermans, W., Elguero, J., Limbach, H.-H. & Aquilar-Parrilla, F. (1994). Acta Cryst. B50, 746-762.]), which contains two of the three mentioned substituents.

[Scheme 1]

In a series of studies on the preparation and hydrogen-bonding properties of 3,4,5-tris­ubstituted pyrazoles, we now report 5-tert-but­yl-4-nitro-1H-pyrazol-3-ol, (I)[link]. The structure of (I)[link] (Fig. 1[link]) consists of mol­ecules that pack to form a linear hydrogen-bonded ribbon motif (Fig. 2[link]). The hydrogen-bonding arrangement can be described by two centrosymmetric dimer formations (Table 1[link]). The first of these dimer formations is atypical of pyrazoles and involves an N1—H⋯N2 inter­action, centred at ([{1\over 2}],0,0) described by an R22(6) graph set (Etter, 1990[Etter, M. C. (1990). Acc. Chem. Res. 23, 120-126.]), while the second dimer formation, centred at (0,1,0), involves one intra­molecular hydrogen-bonding association from O3—H to O42, forming an S(6) graph-set motif, and an R22(4) graph-set motif arising from the three-centre association involving H3 and two O42 atoms. The other O atom (O41) of the nitro group is not involved in the hydrogen-bond network. The ribbon motifs are stacked in the a-axis direction, the perpendicular distances between ribbon planes being 3.263 (2) and 3.195 (2) Å (calculated with PLATON; Spek, 2003[Spek, A. L. (2003). J. Appl. Cryst. 36, 7-13.]).

[Figure 1]
Figure 1
The mol­ecular configuration and atom-numbering scheme for (I)[link]. Displacement ellipsoids are drawn at the 50% probability level. H atoms are drawn as spheres of arbitrary radius.
[Figure 2]
Figure 2
A partial packing diagram for (I)[link], showing the hydrogen-bonded (dashed lines) ribbon motif. For clarity, H atoms not involved in the hydrogen-bonding inter­actions have been omitted. [Symmetry codes: (i) −x + 1, −y, −z and (ii) −x, −y + 2, −z.]

Experimental

Synthetically, (I)[link] originated from 3,5-di-tert-butyl­pyrazole, being produced by gently warming this compound in concentrated nitric acid. In this reaction, 3,5-di-tert-butyl­pyrazole is attacked by nitric acid to form the onium species, which then displaces one tert-but­yl group. The subsequent vacant position is then filled by an OH group that does not tautomerize to form the pyrazolone. The title compound was obtained from Key Organics Ltd and crystals were grown from ethanol solution.

Crystal data
  • C7H11N3O3

  • Mr = 185.19

  • Triclinic, [P \overline 1]

  • a = 6.4870 (5) Å

  • b = 6.6560 (4) Å

  • c = 11.5588 (8) Å

  • α = 81.227 (4)°

  • β = 76.733 (3)°

  • γ = 65.037 (5)°

  • V = 439.50 (6) Å3

  • Z = 2

  • Dx = 1.399 Mg m−3

  • Mo Kα radiation

  • Cell parameters from 1899 reflections

  • θ = 2.9–27.5°

  • μ = 0.11 mm−1

  • T = 120 (2) K

  • Plate, colourless

  • 0.30 × 0.05 × 0.01 mm

Data collection
  • Bruker Nonius KappaCCD diffractometer

  • φ and ω scans

  • Absorption correction: multi-scan(SADABS; Sheldrick, 2003[Sheldrick, G. M. (2003). SADABS. Version 2.10. Bruker AXS Inc., Madison, Wisconsin, USA.])Tmin = 0.968, Tmax = 0.999

  • 7496 measured reflections

  • 1720 independent reflections

  • 1494 reflections with I > 2σ(I)

  • Rint = 0.054

  • θmax = 26.0°

  • h = −7 → 7

  • k = −7 → 8

  • l = −14 → 14

Refinement
  • Refinement on F2

  • R[F2 > 2σ(F2)] = 0.059

  • wR(F2) = 0.153

  • S = 1.19

  • 1720 reflections

  • 128 parameters

  • H atoms treated by a mixture of independent and constrained refinement

  • w = 1/[σ2(Fo2) + (0.0798P)2 + 0.125P] where P = (Fo2 + 2Fc2)/3

  • (Δ/σ)max = 0.001

  • Δρmax = 0.47 e Å−3

  • Δρmin = −0.43 e Å−3

  • Extinction correction: SHELXL97

  • Extinction coefficient: 0.28 (3)

Table 1
Hydrogen-bond geometry (Å, °)[link]

D—H⋯A D—H H⋯A DA D—H⋯A
N1—H1⋯N2i 0.88 (3) 2.09 (3) 2.847 (2) 144 (2)
O3—H3⋯O42 0.87 (3) 2.02 (3) 2.718 (2) 136 (2)
O3—H3⋯O42ii 0.87 (3) 2.19 (3) 2.948 (2) 145 (2)
Symmetry codes: (i) -x+1, -y, -z; (ii) -x, -y+2, -z.

All tert-but­yl H atoms were included in the refinement at calculated positions, in the riding-model approximation, with C—H distances of 0.98 Å. All H atoms involved in the hydrogen-bonding associations were located in Fourier syntheses and positional parameters were refined. The isotropic displacement parameters for all H atoms were set equal to 1.25Ueq of the carrier atom.

Data collection: COLLECT (Hooft, 1998[Hooft, R. W. W. (1998). COLLECT. Nonius BV, Delft, The Netherlands.]); cell refinement: DENZO (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology. Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]) and COLLECT; data reduction: DENZO and COLLECT; 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: PLATON (Spek, 2003[Spek, A. L. (2003). J. Appl. Cryst. 36, 7-13.]); software used to prepare material for publication: SHELXL97.

Supporting information


Comment top

Pyrazole or associated compounds, are common molecules used in coordination or organometallic chemistry as bridging ligands, utilizing the ring positions of the two N atoms. There are 1388 structures in the Cambridge Structural Database (CSD; Version 5.26, November 2004; Allen, 2002), that contain a pyrazole moiety with the extra search constraints `no extra cyclic routes' and `require 3 d coordinates'. This number reduces to 23 for 4-nitropyrazoles, 80 for 5-tert-butylpyrazoles, and 15 for 3-hydroxypyrazoles. Interestingly, there is only one structure (CSD refcode: WILBAU), that of 3,5-di-tert-butyl-4-nitropyrazole (Llamas-Saiz et al., 1994), which contains two of the three mentioned substituents.

In a series of studies on the preparation and hydrogen-bonding properties of 3,4,5-trisubstituted pyrazoles, we now report 5-tert-butyl-4-nitro-1H-pyrazol-3-ol, (I). The structure of (I) (Fig. 1) consists of molecules that pack to form a linear hydrogen-bonded ribbon motif (Fig. 2). The hydrogen-bonding arrangement can be described by two centrosymmetric dimer formations (Table 1). The first of these dimer formations is atypical of pyrazoles and involves an N1—H···N2 interaction, centred at (1/2,0,0) described by an R22(6) graph set (Etter, 1990), while the second dimer formation, centred at (0,1,0), involves one intramolecular hydrogen-bonding association from O3—H to O42, forming an S(6) graph-set motif, and an R22(4) graph-set motif arising from the three-centre association involving H3 and two O42 atoms. The other O atom (O41) of the nitro group is not involved in the hydrogen-bond network. The ribbon motifs are stacked in the a-cell direction, the perpendicular distances between ribbon planes being 3.263 (2) and 3.195 (2) Å (calculated with PLATON; Spek, 2003).

Experimental top

Synthetically, (I) originated from 3,5-di-tert-butylpyrazole, being produced by gently warming this compound in concentrated nitric acid. In this reaction, 3,5-di-tert-butylpyrazole is attacked by nitric acid to form the onium species, which then displaces one tert-butyl group. The subsequent vacant position is then filled by an OH group that does not tautomerize to form the pyrazolone. The title compound was however obtained from Key Organics Ltd and crystals were grown from ethanol solution.

Refinement top

All tert-butyl H atoms were included in the refinement at calculated positions, in the riding-model approximation, with C—H distances of 0.98 Å. All H atoms involved in the hydrogen-bonding associations were located on Fourier syntheses and positional parameters were refined. The isotropic displacement parameters for all H atoms were set equal to 1.25Ueq of the carrier atom.

Computing details top

Data collection: COLLECT (Hooft, 1998); cell refinement: DENZO (Otwinowski & Minor, 1997) and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The molecular configuration and atom-numbering scheme for (I). Displacement ellipsoids are drawn at the 50% probability level. H atoms are drawn as spheres of arbitrary radius.
[Figure 2] Fig. 2. The partial packing diagram for (I), showing the hydrogen-bonded (dashed lines) ribbon motif. For clarity, H atoms not involved in the hydrogen-bonding interactions have been omitted. [Symmetry codes: (i) -x + 1, -y, -z and (ii) -x, -y + 2, -z.]
5-tert-butyl-4-nitro-1H-pyrazol-3-ol top
Crystal data top
C7H11N3O3Z = 2
Mr = 185.19F(000) = 196
Triclinic, P1Dx = 1.399 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 6.4870 (5) ÅCell parameters from 1899 reflections
b = 6.6560 (4) Åθ = 2.9–27.5°
c = 11.5588 (8) ŵ = 0.11 mm1
α = 81.227 (4)°T = 120 K
β = 76.733 (3)°Plate, colourless
γ = 65.037 (5)°0.30 × 0.05 × 0.01 mm
V = 439.50 (6) Å3
Data collection top
Bruker Nonius 95 mm CCD camera on κ-goniostat
diffractometer
1720 independent reflections
Radiation source: Bruker Nonius FR591 rotating anode1494 reflections with I > 2σ(I)
10 cm confocal mirrors monochromatorRint = 0.054
Detector resolution: 9.091 pixels mm-1θmax = 26.0°, θmin = 3.4°
ϕ and ω scansh = 77
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
k = 78
Tmin = 0.968, Tmax = 0.999l = 1414
7496 measured reflections
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)] = 0.059H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.153 w = 1/[σ2(Fo2) + (0.0798P)2 + 0.125P]
where P = (Fo2 + 2Fc2)/3
S = 1.19(Δ/σ)max = 0.001
1720 reflectionsΔρmax = 0.47 e Å3
128 parametersΔρmin = 0.43 e Å3
0 restraintsExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.28 (3)
Crystal data top
C7H11N3O3γ = 65.037 (5)°
Mr = 185.19V = 439.50 (6) Å3
Triclinic, P1Z = 2
a = 6.4870 (5) ÅMo Kα radiation
b = 6.6560 (4) ŵ = 0.11 mm1
c = 11.5588 (8) ÅT = 120 K
α = 81.227 (4)°0.30 × 0.05 × 0.01 mm
β = 76.733 (3)°
Data collection top
Bruker Nonius 95 mm CCD camera on κ-goniostat
diffractometer
1720 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
1494 reflections with I > 2σ(I)
Tmin = 0.968, Tmax = 0.999Rint = 0.054
7496 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0590 restraints
wR(F2) = 0.153H atoms treated by a mixture of independent and constrained refinement
S = 1.19Δρmax = 0.47 e Å3
1720 reflectionsΔρmin = 0.43 e Å3
128 parameters
Special details top

Experimental. The minimum and maximum absorption values stated above are those calculated in SHELXL97 from the given crystal dimensions. The ratio of minimum to maximum apparent transmission was determined experimentally as 0.742732.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.3670 (3)0.1639 (3)0.10021 (14)0.0270 (4)
H10.438 (4)0.018 (4)0.108 (2)0.034*
N20.3749 (3)0.2670 (3)0.01267 (14)0.0275 (4)
C30.2598 (3)0.4796 (3)0.00586 (17)0.0256 (5)
O30.2342 (2)0.6286 (2)0.08679 (12)0.0306 (4)
H30.166 (4)0.761 (4)0.059 (2)0.038*
C40.1789 (3)0.5110 (3)0.12948 (16)0.0249 (5)
N410.0462 (3)0.7199 (3)0.17586 (15)0.0296 (4)
O410.0311 (2)0.7382 (2)0.28295 (13)0.0371 (4)
O420.0128 (3)0.8841 (2)0.10277 (14)0.0413 (5)
C50.2535 (3)0.2983 (3)0.18861 (17)0.0250 (5)
C510.2309 (3)0.2081 (3)0.31659 (17)0.0287 (5)
C520.3656 (4)0.0443 (3)0.32335 (19)0.0351 (5)
H510.30380.11200.27800.044*
H520.35000.10180.40670.044*
H530.52940.08070.28970.044*
C530.0255 (3)0.2613 (4)0.36904 (19)0.0356 (5)
H540.11530.42200.36160.044*
H550.04150.20930.45330.044*
H560.08320.18630.32570.044*
C540.3329 (4)0.3093 (4)0.38784 (19)0.0397 (6)
H570.49710.26960.35400.050*
H580.31660.25140.47110.050*
H590.25000.47120.38390.050*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0287 (9)0.0183 (8)0.0280 (9)0.0040 (6)0.0050 (7)0.0006 (6)
N20.0303 (9)0.0207 (9)0.0261 (9)0.0059 (7)0.0040 (7)0.0005 (6)
C30.0232 (9)0.0219 (9)0.0290 (10)0.0063 (7)0.0064 (7)0.0001 (7)
O30.0339 (8)0.0206 (7)0.0317 (8)0.0057 (6)0.0078 (6)0.0018 (6)
C40.0218 (9)0.0194 (10)0.0295 (10)0.0038 (7)0.0052 (7)0.0026 (7)
N410.0261 (8)0.0223 (9)0.0356 (10)0.0043 (6)0.0064 (7)0.0035 (7)
O410.0372 (8)0.0310 (8)0.0352 (9)0.0069 (6)0.0012 (6)0.0118 (6)
O420.0488 (10)0.0195 (7)0.0431 (10)0.0025 (6)0.0081 (7)0.0007 (6)
C50.0206 (9)0.0225 (9)0.0296 (10)0.0053 (7)0.0051 (7)0.0038 (7)
C510.0252 (10)0.0283 (10)0.0283 (10)0.0073 (8)0.0049 (8)0.0003 (8)
C520.0335 (11)0.0306 (11)0.0333 (11)0.0077 (9)0.0062 (9)0.0043 (8)
C530.0302 (11)0.0339 (11)0.0354 (11)0.0095 (9)0.0001 (8)0.0006 (9)
C540.0398 (12)0.0468 (13)0.0339 (12)0.0156 (10)0.0116 (9)0.0039 (9)
Geometric parameters (Å, º) top
N1—C51.328 (3)C51—C521.531 (3)
N1—N21.379 (2)C51—C541.538 (3)
N1—H10.88 (3)C51—C531.538 (3)
N2—C31.316 (2)C52—H510.98
C3—O31.333 (2)C52—H520.98
C3—C41.420 (3)C52—H530.98
O3—H30.87 (3)C53—H540.98
C4—N411.402 (2)C53—H550.98
C4—C51.409 (3)C53—H560.98
N41—O411.228 (2)C54—H570.98
N41—O421.248 (2)C54—H580.98
C5—C511.508 (3)C54—H590.98
C5—N1—N2115.54 (16)C52—C51—C53108.58 (16)
C5—N1—H1126.1 (15)C54—C51—C53111.13 (17)
N2—N1—H1118.4 (15)C51—C52—H51109.5
C3—N2—N1103.85 (15)C51—C52—H52109.5
N2—C3—O3119.47 (17)H51—C52—H52109.5
N2—C3—C4110.65 (17)C51—C52—H53109.5
O3—C3—C4129.88 (17)H51—C52—H53109.5
C3—O3—H3107.6 (16)H52—C52—H53109.5
N41—C4—C5129.88 (17)C51—C53—H54109.5
N41—C4—C3123.47 (17)C51—C53—H55109.5
C5—C4—C3106.64 (16)H54—C53—H55109.5
O41—N41—O42122.35 (16)C51—C53—H56109.5
O41—N41—C4121.21 (16)H54—C53—H56109.5
O42—N41—C4116.44 (16)H55—C53—H56109.5
N1—C5—C4103.32 (16)C51—C54—H57109.5
N1—C5—C51121.22 (17)C51—C54—H58109.5
C4—C5—C51135.46 (17)H57—C54—H58109.5
C5—C51—C52109.91 (16)C51—C54—H59109.5
C5—C51—C54109.69 (16)H57—C54—H59109.5
C52—C51—C54108.19 (16)H58—C54—H59109.5
C5—C51—C53109.32 (15)
C5—N1—N2—C30.2 (2)N2—N1—C5—C51179.91 (15)
N1—N2—C3—O3179.93 (15)N41—C4—C5—N1178.52 (17)
N1—N2—C3—C40.2 (2)C3—C4—C5—N10.03 (19)
N2—C3—C4—N41178.50 (16)N41—C4—C5—C511.5 (3)
O3—C3—C4—N411.2 (3)C3—C4—C5—C51179.94 (19)
N2—C3—C4—C50.2 (2)N1—C5—C51—C523.3 (2)
O3—C3—C4—C5179.83 (18)C4—C5—C51—C52176.7 (2)
C5—C4—N41—O412.5 (3)N1—C5—C51—C54122.10 (19)
C3—C4—N41—O41175.83 (17)C4—C5—C51—C5457.9 (3)
C5—C4—N41—O42177.17 (18)N1—C5—C51—C53115.81 (19)
C3—C4—N41—O424.5 (3)C4—C5—C51—C5364.2 (3)
N2—N1—C5—C40.1 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···N2i0.88 (3)2.09 (3)2.847 (2)144 (2)
O3—H3···O420.87 (3)2.02 (3)2.718 (2)136 (2)
O3—H3···O42ii0.87 (3)2.19 (3)2.948 (2)145 (2)
Symmetry codes: (i) x+1, y, z; (ii) x, y+2, z.

Experimental details

Crystal data
Chemical formulaC7H11N3O3
Mr185.19
Crystal system, space groupTriclinic, P1
Temperature (K)120
a, b, c (Å)6.4870 (5), 6.6560 (4), 11.5588 (8)
α, β, γ (°)81.227 (4), 76.733 (3), 65.037 (5)
V3)439.50 (6)
Z2
Radiation typeMo Kα
µ (mm1)0.11
Crystal size (mm)0.30 × 0.05 × 0.01
Data collection
DiffractometerBruker Nonius 95 mm CCD camera on κ-goniostat
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 2003)
Tmin, Tmax0.968, 0.999
No. of measured, independent and
observed [I > 2σ(I)] reflections
7496, 1720, 1494
Rint0.054
(sin θ/λ)max1)0.617
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.059, 0.153, 1.19
No. of reflections1720
No. of parameters128
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.47, 0.43

Computer programs: COLLECT (Hooft, 1998), DENZO (Otwinowski & Minor, 1997) and COLLECT, DENZO and COLLECT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 2003), SHELXL97.

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···N2i0.88 (3)2.09 (3)2.847 (2)144 (2)
O3—H3···O420.87 (3)2.02 (3)2.718 (2)136 (2)
O3—H3···O42ii0.87 (3)2.19 (3)2.948 (2)145 (2)
Symmetry codes: (i) x+1, y, z; (ii) x, y+2, z.
 

Acknowledgements

The authors thank the EPSRC National Crystallography Service (Southampton, England) and acknowledge the use of the EPSRC's Chemical Database Service at Daresbury Laboratory (Fletcher et al., 1996[Fletcher, D. A., McMeeking, R. F. & Parkin, D. J. (1996). J. Chem. Inf. Comput. Sci. 36, 746-749.]).

References

First citationAllen, F. H. (2002). Acta Cryst. B58, 380–388. Web of Science CrossRef CAS IUCr Journals
First citationEtter, M. C. (1990). Acc. Chem. Res. 23, 120–126. CrossRef CAS Web of Science
First citationFletcher, D. A., McMeeking, R. F. & Parkin, D. J. (1996). J. Chem. Inf. Comput. Sci. 36, 746–749. CrossRef CAS Web of Science
First citationHooft, R. W. W. (1998). COLLECT. Nonius BV, Delft, The Netherlands.
First citationLlamas-Saiz, A. L., Foces-Foces, C., Cano, F. H., Jimenez, P., Laynez, J., Meutermans, W., Elguero, J., Limbach, H.-H. & Aquilar-Parrilla, F. (1994). Acta Cryst. B50, 746–762. CSD CrossRef CAS Web of Science IUCr Journals
First citationOtwinowski, Z. & Minor, W. (1997). Methods in Enzymology. Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307–326. New York: Academic Press.
First citationSheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.
First citationSheldrick, G. M. (2003). SADABS. Version 2.10. Bruker AXS Inc., Madison, Wisconsin, USA.
First citationSpek, A. L. (2003). J. Appl. Cryst. 36, 7–13. Web of Science CrossRef CAS IUCr Journals

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