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

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ISSN: 2056-9890

Ammonium di­hydrogen (1-ammonio­pentane-1,1-di­yl)di­phospho­nate

aInstitute of General and Inorganic Chemistry, NAS Ukraine Kyiv, Prosp. Palladina 32/34, 03680 Ukraine
*Correspondence e-mail: dudco_anatolij@ukr.net

(Received 14 July 2009; accepted 17 July 2009; online 22 July 2009)

The title compound, NH4+·C5H14NO6P2, was obtained from 1-ammonio-1-phosphono­pentane-1-phospho­nic acid and ammonium hydroxide in aqueous solution. The asymmetric unit of title compound contains one molecule, which consists of an ammonium cation and an aminodiphosphonic anion with the H atoms transferred from the phosphonic acid group to the amino group. The crystal structure shows a three-dimensional network of O—H⋯O and N—H⋯O hydrogen bonds which stabilize the structure.

Related literature

For general background to the use of organic diphospho­nic acids as chelating agents in metal extraction and as drugs to prevent calcification and inhibit bone resorption, see: Matczak-Jon & Videnova-Adrabinska (2005[Matczak-Jon, E. & Videnova-Adrabinska, V. (2005). Coord. Chem. Rev. 249, 2458-2488.]); Tromelin et al. (1986[Tromelin, A., El Manouni, D. & Burgada, R. (1986). Phosphorus Sulfur Relat. Elem. 27, 301-312.]); Szabo et al. (2002[Szabo, Ch. M., Martin, M. B. & Oldfield, E. (2002). J. Med. Chem. 45, 2894-2903.]). For related structures, see: Bon et al. (2008[Bon, V. V., Dudko, A. V., Kozachkova, A. N. & Pekhnyo, V. I. (2008). Acta Cryst. E64, o2436.]). For bond–length data, see: Allen et al. (1987[Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1-19.]).

[Scheme 1]

Experimental

Crystal data
  • NH4+·C5H14NO6P2

  • Mr = 264.15

  • Monoclinic, P 21 /c

  • a = 9.6007 (6) Å

  • b = 5.7239 (4) Å

  • c = 20.3259 (15) Å

  • β = 98.100 (3)°

  • V = 1105.84 (13) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.41 mm−1

  • T = 296 K

  • 0.50 × 0.12 × 0.04 mm

Data collection
  • Bruker APEXII CCD diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2005[Bruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.824, Tmax = 0.982

  • 5297 measured reflections

  • 2256 independent reflections

  • 1532 reflections with I > 2σ(I)

  • Rint = 0.056

Refinement
  • R[F2 > 2σ(F2)] = 0.051

  • wR(F2) = 0.122

  • S = 1.02

  • 2256 reflections

  • 173 parameters

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

  • Δρmax = 0.37 e Å−3

  • Δρmin = −0.38 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N1—H11N⋯O2i 1.05 (4) 1.75 (4) 2.777 (4) 163 (3)
N1—H13N⋯O3ii 0.93 (4) 1.98 (4) 2.828 (4) 152 (3)
N1—H12N⋯O6i 0.93 (5) 2.08 (5) 2.879 (4) 143 (4)
O3—H3O⋯O5ii 0.80 (5) 1.72 (5) 2.519 (4) 174 (5)
O4—H4O⋯O6iii 0.82 (5) 1.75 (5) 2.566 (3) 173 (5)
N2—H22N⋯O1iv 0.86 (4) 1.95 (4) 2.781 (4) 161 (4)
N2—H21N⋯O2 1.02 (6) 1.77 (6) 2.769 (4) 165 (4)
N2—H23N⋯O5v 0.93 (6) 2.07 (6) 2.787 (5) 134 (5)
N2—H24N⋯O1vi 0.92 (5) 1.83 (5) 2.705 (5) 159 (4)
Symmetry codes: (i) x, y-1, z; (ii) [-x, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]; (iii) -x, -y+1, -z+1; (iv) [-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]; (v) [-x, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]; (vi) x, y+1, z.

Data collection: APEX2 (Bruker, 2005[Bruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2005[Bruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: publCIF (Westrip, 2009[Westrip, S. P. (2009). publCIF. In preparation.]).

Supporting information


Comment top

The organic diphosphonic acids are potentially very powerful chelating agents used in metal extractions and are tested by the pharmaceutical industry for use as efficient drugs preventing calcification and inhibiting bone resorption (Tromelin et al., 1986, Matczak-Jon & Videnova-Adrabinska, 2005). Diphosphonic acids are used in the treatment of Paget disease, osteoporosis and tumoral osteolysis (Szabo et al., 2002). The asymmetric unit of title compound (Fig. 1) contains one molecule, which exists as anion with protons transferred from the phosphonic group to the amino group. The ammonium cation attendant in structure neutralizes the negatively charged phosphonic acid residual. The phosphorus atom displays a slightly distorted tetrahedral geometry provided by three oxygen atoms and one carbon atom. Bond lengths and angles have normal values (Allen et al., 1987). The crystal structure of title compound shows three–dimensional network of O—H···O and N—H···O hydrogen bonds which additionally stabilized the structure (Table 1, Fig. 2).

Related literature top

For general background to the use of organic diphosphonic acids as chelating agents in metal extraction and as drugs to prevent calcification and inhibit bone resorption, see: Matczak-Jon & Videnova-Adrabinska (2005); Tromelin et al. (1986); Szabo et al. (2002). For related structures, see: Bon et al. (2008). For bond–length data, see: Allen et al. (1987).

Experimental top

The title compound was obtained by the reaction of 1–ammonio–1–phosphonopentane–1–phosphonic acid and ammonium hydroxide (1:1) in the aqueous solution. The solution was left at room temperature. Colourless crystals of the title compound were obtained after 5 days staying.

Refinement top

The H atoms bonded to O and N atoms were located in a difference map and refined freely. Other H atoms which bonded to C were positioned geometrically and refined using a riding model with C—H = 0.96 Å for CH3 with Uiso(H) = 1.5Ueq(C) and C—H = 0.97 Å for CH2 with Uiso(H) = 1.2Ueq(C).

Computing details top

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: publCIF (Westrip, 2009).

Figures top
[Figure 1] Fig. 1. The asymmetric unit of title compound with the atom numbering scheme. Displacement ellipsoids are drawn at 50% probability level. Hydrogen atoms are presented as a small spheres of arbitrary rAdius.
[Figure 2] Fig. 2. Crystal packing of title compound, projection along b axis. Dashed lines indicate hydrogen bonds.
Ammonium dihydrogen (1-ammoniopentane-1,1-diyl)diphosphonate top
Crystal data top
NH4+·C5H14NO6P2F(000) = 560
Mr = 264.15Dx = 1.587 Mg m3
Monoclinic, P21/cMelting point: 495 K
Hall symbol: -P 2ybcMo Kα radiation, λ = 0.71073 Å
a = 9.6007 (6) ÅCell parameters from 824 reflections
b = 5.7239 (4) Åθ = 2.7–21.1°
c = 20.3259 (15) ŵ = 0.41 mm1
β = 98.100 (3)°T = 296 K
V = 1105.84 (13) Å3Needle, colourless
Z = 40.50 × 0.12 × 0.04 mm
Data collection top
Bruker APEXII CCD
diffractometer
2256 independent reflections
Radiation source: fine–focus sealed tube1532 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.056
Detector resolution: 8.26 pixels mm-1θmax = 26.4°, θmin = 2.0°
ϕ and ω scansh = 1111
Absorption correction: multi-scan
(SADABS; Bruker, 2005)
k = 75
Tmin = 0.824, Tmax = 0.982l = 2425
5297 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.051Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.122H atoms treated by a mixture of independent and constrained refinement
S = 1.02 w = 1/[σ2(Fo2) + (0.0435P)2 + 0.4298P]
where P = (Fo2 + 2Fc2)/3
2256 reflections(Δ/σ)max < 0.001
173 parametersΔρmax = 0.37 e Å3
0 restraintsΔρmin = 0.38 e Å3
Crystal data top
NH4+·C5H14NO6P2V = 1105.84 (13) Å3
Mr = 264.15Z = 4
Monoclinic, P21/cMo Kα radiation
a = 9.6007 (6) ŵ = 0.41 mm1
b = 5.7239 (4) ÅT = 296 K
c = 20.3259 (15) Å0.50 × 0.12 × 0.04 mm
β = 98.100 (3)°
Data collection top
Bruker APEXII CCD
diffractometer
2256 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2005)
1532 reflections with I > 2σ(I)
Tmin = 0.824, Tmax = 0.982Rint = 0.056
5297 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0510 restraints
wR(F2) = 0.122H atoms treated by a mixture of independent and constrained refinement
S = 1.02Δρmax = 0.37 e Å3
2256 reflectionsΔρmin = 0.38 e Å3
173 parameters
Special details top

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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
P10.22481 (10)0.43513 (17)0.29915 (4)0.0195 (3)
P20.00587 (9)0.47871 (16)0.39608 (4)0.0184 (2)
C10.1590 (3)0.3149 (6)0.37310 (16)0.0161 (7)
C20.2832 (4)0.3109 (7)0.43011 (17)0.0243 (8)
H2A0.36350.24390.41290.029*
H2B0.30700.47150.44210.029*
C30.2649 (4)0.1806 (7)0.49344 (17)0.0295 (9)
H3A0.17870.23160.50880.035*
H3B0.25670.01460.48410.035*
C40.3877 (4)0.2227 (8)0.54735 (18)0.0374 (11)
H4A0.38850.38600.56020.045*
H4B0.47450.19090.52970.045*
C50.3827 (5)0.0731 (9)0.6084 (2)0.0506 (13)
H5A0.29850.10740.62710.076*
H5B0.46340.10590.64070.076*
H5C0.38310.08890.59620.076*
N10.1106 (3)0.0689 (5)0.35619 (16)0.0200 (7)
N20.3682 (4)0.9144 (7)0.2109 (2)0.0297 (8)
O10.3514 (2)0.2924 (4)0.28929 (11)0.0247 (6)
O20.2493 (3)0.6898 (4)0.31012 (12)0.0279 (6)
O30.1056 (3)0.3928 (5)0.23993 (12)0.0282 (7)
O40.0725 (3)0.2932 (4)0.43385 (13)0.0263 (6)
O50.0902 (2)0.5374 (5)0.33383 (12)0.0280 (6)
O60.0601 (3)0.6800 (4)0.43945 (11)0.0237 (6)
H3O0.107 (5)0.279 (9)0.217 (2)0.065 (18)*
H4O0.061 (5)0.303 (9)0.475 (2)0.070 (18)*
H11N0.180 (4)0.059 (7)0.3428 (19)0.047 (12)*
H12N0.078 (5)0.001 (8)0.392 (2)0.060 (14)*
H13N0.038 (4)0.063 (7)0.321 (2)0.040 (12)*
H21N0.336 (5)0.810 (9)0.247 (3)0.083 (18)*
H22N0.449 (5)0.874 (7)0.2012 (19)0.040 (13)*
H23N0.295 (6)0.919 (10)0.176 (3)0.10 (2)*
H24N0.377 (5)1.058 (8)0.231 (2)0.048 (14)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
P10.0216 (5)0.0158 (5)0.0220 (5)0.0005 (4)0.0066 (4)0.0005 (4)
P20.0181 (5)0.0165 (5)0.0213 (5)0.0008 (4)0.0054 (4)0.0007 (4)
C10.0180 (17)0.0085 (18)0.0212 (17)0.0008 (15)0.0006 (14)0.0005 (13)
C20.0189 (18)0.026 (2)0.0263 (19)0.0043 (17)0.0025 (15)0.0006 (16)
C30.028 (2)0.034 (3)0.0250 (19)0.002 (2)0.0005 (17)0.0037 (17)
C40.037 (2)0.043 (3)0.029 (2)0.004 (2)0.0054 (19)0.0001 (19)
C50.052 (3)0.068 (4)0.030 (2)0.011 (3)0.000 (2)0.007 (2)
N10.0237 (16)0.0152 (17)0.0211 (16)0.0026 (14)0.0028 (14)0.0007 (13)
N20.026 (2)0.026 (2)0.040 (2)0.0035 (18)0.0115 (18)0.0002 (17)
O10.0194 (13)0.0244 (15)0.0314 (13)0.0026 (12)0.0074 (11)0.0023 (11)
O20.0360 (15)0.0154 (15)0.0347 (14)0.0015 (13)0.0132 (12)0.0007 (11)
O30.0297 (15)0.0329 (18)0.0216 (13)0.0049 (14)0.0019 (12)0.0045 (13)
O40.0315 (15)0.0229 (16)0.0265 (15)0.0089 (12)0.0108 (12)0.0013 (12)
O50.0198 (12)0.0329 (17)0.0305 (14)0.0030 (12)0.0002 (11)0.0063 (12)
O60.0317 (14)0.0131 (14)0.0278 (13)0.0043 (12)0.0097 (11)0.0040 (10)
Geometric parameters (Å, º) top
P1—O21.488 (3)C4—C51.514 (5)
P1—O11.501 (2)C4—H4A0.9700
P1—O31.559 (3)C4—H4B0.9700
P1—C11.844 (3)C5—H5A0.9600
P2—O51.495 (2)C5—H5B0.9600
P2—O61.499 (2)C5—H5C0.9600
P2—O41.564 (3)N1—H11N1.05 (4)
P2—C11.858 (3)N1—H12N0.93 (5)
C1—N11.507 (4)N1—H13N0.93 (4)
C1—C21.541 (5)N2—H21N1.02 (6)
C2—C31.519 (5)N2—H22N0.86 (4)
C2—H2A0.9700N2—H23N0.93 (6)
C2—H2B0.9700N2—H24N0.92 (5)
C3—C41.511 (5)O3—H3O0.80 (5)
C3—H3A0.9700O4—H4O0.82 (5)
C3—H3B0.9700
O2—P1—O1116.04 (14)C2—C3—H3B109.4
O2—P1—O3110.56 (16)H3A—C3—H3B108.0
O1—P1—O3109.44 (15)C3—C4—C5113.1 (4)
O2—P1—C1107.97 (15)C3—C4—H4A109.0
O1—P1—C1106.42 (15)C5—C4—H4A109.0
O3—P1—C1105.83 (15)C3—C4—H4B109.0
O5—P2—O6116.53 (15)C5—C4—H4B109.0
O5—P2—O4106.61 (15)H4A—C4—H4B107.8
O6—P2—O4112.60 (14)C4—C5—H5A109.5
O5—P2—C1108.42 (14)C4—C5—H5B109.5
O6—P2—C1108.33 (14)H5A—C5—H5B109.5
O4—P2—C1103.51 (14)C4—C5—H5C109.5
N1—C1—C2109.8 (3)H5A—C5—H5C109.5
N1—C1—P1107.0 (2)H5B—C5—H5C109.5
C2—C1—P1107.5 (2)C1—N1—H11N122 (2)
N1—C1—P2107.4 (2)C1—N1—H12N110 (3)
C2—C1—P2112.0 (2)H11N—N1—H12N101 (3)
P1—C1—P2113.01 (17)C1—N1—H13N113 (2)
C3—C2—C1118.3 (3)H11N—N1—H13N102 (3)
C3—C2—H2A107.7H12N—N1—H13N107 (4)
C1—C2—H2A107.7H21N—N2—H22N112 (4)
C3—C2—H2B107.7H21N—N2—H23N107 (4)
C1—C2—H2B107.7H22N—N2—H23N116 (4)
H2A—C2—H2B107.1H21N—N2—H24N103 (4)
C4—C3—C2111.4 (3)H22N—N2—H24N108 (4)
C4—C3—H3A109.4H23N—N2—H24N109 (4)
C2—C3—H3A109.4P1—O3—H3O120 (4)
C4—C3—H3B109.4P2—O4—H4O116 (4)
O2—P1—C1—N1170.1 (2)O5—P2—C1—C2162.9 (2)
O1—P1—C1—N164.7 (2)O6—P2—C1—C235.6 (3)
O3—P1—C1—N151.7 (3)O4—P2—C1—C284.2 (3)
O2—P1—C1—C272.0 (3)O5—P2—C1—P141.3 (2)
O1—P1—C1—C253.2 (3)O6—P2—C1—P186.01 (19)
O3—P1—C1—C2169.6 (2)O4—P2—C1—P1154.25 (17)
O2—P1—C1—P252.1 (2)N1—C1—C2—C353.3 (4)
O1—P1—C1—P2177.27 (16)P1—C1—C2—C3169.4 (3)
O3—P1—C1—P266.4 (2)P2—C1—C2—C365.9 (4)
O5—P2—C1—N176.5 (2)C1—C2—C3—C4171.9 (3)
O6—P2—C1—N1156.2 (2)C2—C3—C4—C5172.9 (3)
O4—P2—C1—N136.4 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H11N···O2i1.05 (4)1.75 (4)2.777 (4)163 (3)
N1—H13N···O3ii0.93 (4)1.98 (4)2.828 (4)152 (3)
N1—H12N···O6i0.93 (5)2.08 (5)2.879 (4)143 (4)
O3—H3O···O5ii0.80 (5)1.72 (5)2.519 (4)174 (5)
O4—H4O···O6iii0.82 (5)1.75 (5)2.566 (3)173 (5)
N2—H22N···O1iv0.86 (4)1.95 (4)2.781 (4)161 (4)
N2—H21N···O21.02 (6)1.77 (6)2.769 (4)165 (4)
N2—H23N···O5v0.93 (6)2.07 (6)2.787 (5)134 (5)
N2—H24N···O1vi0.92 (5)1.83 (5)2.705 (5)159 (4)
Symmetry codes: (i) x, y1, z; (ii) x, y1/2, z+1/2; (iii) x, y+1, z+1; (iv) x+1, y+1/2, z+1/2; (v) x, y+1/2, z+1/2; (vi) x, y+1, z.

Experimental details

Crystal data
Chemical formulaNH4+·C5H14NO6P2
Mr264.15
Crystal system, space groupMonoclinic, P21/c
Temperature (K)296
a, b, c (Å)9.6007 (6), 5.7239 (4), 20.3259 (15)
β (°) 98.100 (3)
V3)1105.84 (13)
Z4
Radiation typeMo Kα
µ (mm1)0.41
Crystal size (mm)0.50 × 0.12 × 0.04
Data collection
DiffractometerBruker APEXII CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2005)
Tmin, Tmax0.824, 0.982
No. of measured, independent and
observed [I > 2σ(I)] reflections
5297, 2256, 1532
Rint0.056
(sin θ/λ)max1)0.626
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.051, 0.122, 1.02
No. of reflections2256
No. of parameters173
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.37, 0.38

Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008), publCIF (Westrip, 2009).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H11N···O2i1.05 (4)1.75 (4)2.777 (4)163 (3)
N1—H13N···O3ii0.93 (4)1.98 (4)2.828 (4)152 (3)
N1—H12N···O6i0.93 (5)2.08 (5)2.879 (4)143 (4)
O3—H3O···O5ii0.80 (5)1.72 (5)2.519 (4)174 (5)
O4—H4O···O6iii0.82 (5)1.75 (5)2.566 (3)173 (5)
N2—H22N···O1iv0.86 (4)1.95 (4)2.781 (4)161 (4)
N2—H21N···O21.02 (6)1.77 (6)2.769 (4)165 (4)
N2—H23N···O5v0.93 (6)2.07 (6)2.787 (5)134 (5)
N2—H24N···O1vi0.92 (5)1.83 (5)2.705 (5)159 (4)
Symmetry codes: (i) x, y1, z; (ii) x, y1/2, z+1/2; (iii) x, y+1, z+1; (iv) x+1, y+1/2, z+1/2; (v) x, y+1/2, z+1/2; (vi) x, y+1, z.
 

References

First citationAllen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19.  CrossRef Web of Science Google Scholar
First citationBon, V. V., Dudko, A. V., Kozachkova, A. N. & Pekhnyo, V. I. (2008). Acta Cryst. E64, o2436.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationBruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationMatczak-Jon, E. & Videnova-Adrabinska, V. (2005). Coord. Chem. Rev. 249, 2458–2488.  Web of Science CrossRef CAS Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSzabo, Ch. M., Martin, M. B. & Oldfield, E. (2002). J. Med. Chem. 45, 2894–2903.  Web of Science CSD CrossRef PubMed CAS Google Scholar
First citationTromelin, A., El Manouni, D. & Burgada, R. (1986). Phosphorus Sulfur Relat. Elem. 27, 301–312.  CrossRef CAS Web of Science Google Scholar
First citationWestrip, S. P. (2009). publCIF. In preparation.  Google Scholar

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