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In the title compound, C6H16N22+·2C2H4O5P-, the cations lie across centres of inversion; in the anions, two of the H-atom sites have 0.50 occupancy. The anions are linked by short O-H...O hydrogen bonds [O...O 2.465 (3)-2.612 (3) Å and O-H...O 165-171°] into sheets of alternating R^2_2(12) and R^6_6(28) rings, both of which are centrosymmetric; the cations lie at the centres of the larger rings linked to the anion sheet by N-H...O hydrogen bonds [N...O 2.642 (2) Å and N-H...O 176°].

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101008022/sk1482sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270101008022/sk1482Isup2.hkl
Contains datablock I

CCDC reference: 170192

Comment top

Phosphonic acids are extremely versatile building blocks in supramolecular chemistry (Ferguson et al., 1998; Glidewell et al., 2000; Wheatley et al., 2001). An important factor in the behaviour of such acids is the marked difference in acidity of the two hydroxyls in the –PO(OH)2 group, such that with organic amines typically only one H per phosphonate is transferred from O to N. The resulting –P(O)2(OH)- group can thus act both as a hydrogen-bond donor and as a hydrogen-bond acceptor. In this respect, singly-ionized phosphonate groups are qualitatively different from ionized carboxyl groups, which can act only as hydrogen-bond acceptors. Seeking to combine, and compare, these two functionalities, we have turned our attention to phosphonoacetic acid (HO)2P(O)CH2COOH.

The structure of phosphonoacetic acid itself [CSD (Allen & Kennard, 1993) code TERLUX; Lis, 1997] contains a three-dimensional hydrogen-bonded framework, dominated by C(4) and C(6) spiral motifs around the screw axes in space group P212121; however the R22(8) motif, so characteristic of carboxylic acids (Sim et al., 1995; Bruno & Randaccio, 1980), as well as phenylphosphonic acid itself (Weakley, 1976) is absent. Rather few examples have been reported of phosphonoacetate salts of other organic moieties. In the 1:1 salt formed with 2-amino-5-nitropyridine (CSD code YISDOT; Pécaud & Masse, 1994), the [C2H4O5P]- anions are built into sheets by just two rather short O—H···O hydrogen bonds, having O···O distances of 2.600 (2) Å and 2.630 (2) Å, and these sheets are linked into a three-dimensional framework by the cations. However, the coordinates in the original paper, and in the CSD, do not represent a connected molecular unit, and those for at least one of the hydroxyl H atoms are seriously in error: hence, detailed analysis of the sheet formation is not appropriate. \sch

The 1:1 adduct (I) formed between N,N'-dimethylpiperazine and phosphonoacetic acid is a salt [{MeN(CH2CH2)2NMe}H2]2+·2[C2H4O5P]- (Fig. 1). The cation lies across a centre of inversion, selected for the sake of convenience as that at (1/2, 1/2, 1/2), while the anion lies in a general position. The ionization of the anion is not straightforward: there is a fully occupied H site adjacent to O3, but the H sites adjacent to O2 and O4 are both half-occupied. Pairs of O2 atoms are linked across centres of inversion: O2 at (x, y, z) acts either as donor to, or as acceptor from, O2 at (2 - x, -y, 3 - z), while O4 at (x, y, z) acts as donor to or acceptor from O4 at (1 - x, 1 - y, 2 - z). In both interactions, the O···O distances are very short, < 2.50 Å (Table 2), approaching the distances typical in O···H···O hydrogen bonds where the H is symmetrically centred between the O atoms (Emsley, 1980). However, for both examples here, involving O2 and O4, careful inspection of difference maps showed clearly that there were two equally occupied off-centre sites.

The O—H···O hydrogen bonds (Table 2) link the anions into a two-dimensional sheet built from alternating R22(12) and R66(28) rings. Phosphonate O3 ar (x, y, z) acts as hydrogen-bond donor to carboxyl O1 at (2 - x, -y, 2 - z), thus producing an R22(12) ring centred at (1, 0, 1) (Fig. 2). The O2···O2i [(i) 2 - x, -y, 3 - z] hydrogen bond links this dimer centred at (1, 0, 1) to similar dimers centred at (1, 0, 0) and (1, 0, 2), while the O4···O4iii [(iii) 1 - x, 1 - y, 2 - z] hydrogen bond links the reference (1, 0, 1) dimer to those centred at (0, 1, 1) and (2, -1, 1). Propagation of the hydrogen bonds by translation thus generates a (110) sheet of anions containing just two types of ring (Fig. 2). The sheets are weakly linked by a single C—H···O hydrogen bond (Table 2). The R22(12) rings are all centred at the vertices of the unit cell and the R66(28) rings are centred at the cell centres, where the cations are located. The two N atoms in the cation centred at (1/2, 1/2, 1/2) are at (x, y, z) and (1 - x, 1 - y, 1 - z) and these act as hydrogen-bond donors to O5 atoms, also at (x, y, z) and (1 - x, 1 - y, 1 - z), respectively, on opposite sides of the R66(28) rings (Fig. 2).

The sheet structure formed by the anions in (I) may be contrasted with the anion aggregation in the corresponding anhydrous lithium and ammonium salts. In the lithium salt (CSD code TERMOS; Lis, 1997), the anions are linked into head-to-head chains containing centrosymmetric R22(8) rings formed by the phosphonate units in adjacent anions and centrosymmetric R22(12) rings formed by carboxyl donor and phosphonate acceptors: as in the parent acid, the carboxyl R22(8) motif is absent. By contrast, in the ammonium salt (CSD code TERMIM; Lis, 1997), the anion are linked into sheets formed by linking R22(8) phosphonate dimers. As noted above this motif is absent in compound (I), where the large rings may be regarded as templated by the cations.

The three independent P—O distances show marked variation (Table 1): P1—O3, which is associated with the fully ordered H is the longest and P1—O5 with no H involvement is the shortest. Similarly, C1—O1, with no H involvement, is significantly shorter than C1—O2, associated with disordered H. The O—P—O and O—C—O angles also reflect the H site occupancies. The O1—C1—O2 and C1—C2—P1 planes are approximately orthogonal, while O5 is antiperiplanar to the carboxyl group (Table 1). In the cation, the methyl groups occupy equatorial sites, as expected, and the three independent C—N distances are identical within experimental uncertainty.

Related literature top

For related literature, see: Allen & Kennard (1993); Bruno & Randaccio (1980); Emsley (1980); Ferguson et al. (1998); Glidewell et al. (2000); Lis (1997); Pécaud & Masse (1994); Weakley (1976); Wheatley et al. (2001).

Experimental top

Stoichiometric quantities of phosphonoacetic acid and N, N'-dimethylpiperazine were separately dissolved in methanol. The solutions were mixed, and the mixture was set aside to crystallize, producing analytically pure (I). Analysis: found C 30.5, H 6.2, N 7.1%; C10H24N2O10P2 requires C 30.5, H 6.1, N 7.1%. Crystals suitable for single-crystal X-ray diffraction were selected directly from the analytical sample.

Refinement top

Compound (I) crystallized in the triclinic system; space group P1 was assumed and confirmed by the analysis. H atoms were treated as riding atoms with C—H 0.96 Å (CH3) or 0.97 Å (CH2), N—H 0.91 Å and O—H 0.82 Å.

Computing details top

Data collection: Collect (Nonius, 1997-2000); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2001); software used to prepare material for publication: SHELXL97 and PRPKAPPA (Ferguson, 1999).

Figures top
[Figure 1] Fig. 1. The molecular components of (I) showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. The atom marked "a" is at the symmetry position (1 - x, 1 - y, 1 - z), and the H atom sites adjacent to O2 and O4 both have 0.50 occupancy.
[Figure 2] Fig. 2. Part of the crystal structure of (I) showing formation of a (110) sheet of anions with the cations at the centres of the R66(28) rings. For the sake of clarity H atoms bonded to C are omitted. Atoms labelled with a star (*), hash (#), dollar sign () or ampersand (&) are at the symmetry positions (2 - x, -y, 2 - z), (1 - x, 1 - y, 2 - z), (1 - x, 1 - y, - z) and (x, y, -1 + z), respectively.
N,N'-Dimethylpiperazinium (2+) phosphonoacetate top
Crystal data top
C6H16N22+·2C2H4O5PZ = 1
Mr = 394.25F(000) = 208
Triclinic, P1Dx = 1.575 Mg m3
a = 5.9217 (4) ÅMo Kα radiation, λ = 0.71073 Å
b = 8.9858 (5) ÅCell parameters from 1719 reflections
c = 8.9987 (6) Åθ = 2.7–27.6°
α = 61.730 (3)°µ = 0.32 mm1
β = 81.885 (3)°T = 293 K
γ = 81.448 (4)°Plate, colourless
V = 415.65 (5) Å30.34 × 0.20 × 0.06 mm
Data collection top
Kappa-CCD
diffractometer
1900 independent reflections
Radiation source: fine-focus sealed X-ray tube1320 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.045
ϕ scans, and ω scans with κ offsetsθmax = 27.6°, θmin = 2.7°
Absorption correction: multi-scan
(DENZO-SMN; Otwinowski & Minor, 1997)
h = 07
Tmin = 0.900, Tmax = 0.981k = 1111
5103 measured reflectionsl = 1111
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)] = 0.045H-atom parameters constrained
wR(F2) = 0.125 w = 1/[σ2(Fo2) + (0.0458P)2 + 0.1391P]
where P = (Fo2 + 2Fc2)/3
S = 1.04(Δ/σ)max = 0.034
1900 reflectionsΔρmax = 0.26 e Å3
114 parametersΔρmin = 0.39 e Å3
0 restraintsExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.021 (7)
Crystal data top
C6H16N22+·2C2H4O5Pγ = 81.448 (4)°
Mr = 394.25V = 415.65 (5) Å3
Triclinic, P1Z = 1
a = 5.9217 (4) ÅMo Kα radiation
b = 8.9858 (5) ŵ = 0.32 mm1
c = 8.9987 (6) ÅT = 293 K
α = 61.730 (3)°0.34 × 0.20 × 0.06 mm
β = 81.885 (3)°
Data collection top
Kappa-CCD
diffractometer
1900 independent reflections
Absorption correction: multi-scan
(DENZO-SMN; Otwinowski & Minor, 1997)
1320 reflections with I > 2σ(I)
Tmin = 0.900, Tmax = 0.981Rint = 0.045
5103 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0450 restraints
wR(F2) = 0.125H-atom parameters constrained
S = 1.04Δρmax = 0.26 e Å3
1900 reflectionsΔρmin = 0.39 e Å3
114 parameters
Special details top

Experimental. The program DENZO-SMN (Otwinowski & Minor, 1997) uses a scaling algorithm [Fox, G·C. & Holmes, K·C. (1966). Acta Cryst. 20, 886–891] which effectively corrects for absorption effects. High redundancy data were used in the scaling program hence the 'multi-scan' code word was used. No transmission coefficients are available from the program (only scale factors for each frame). The scale factors in the experimental table are calculated from the 'size' command in the SHELXL97 input file.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
N10.5601 (3)0.6266 (2)0.5401 (2)0.0274 (5)
C120.6665 (4)0.6108 (3)0.3874 (3)0.0306 (5)
C130.6746 (4)0.4316 (3)0.4141 (3)0.0316 (6)
C140.5598 (5)0.8030 (3)0.5151 (4)0.0390 (6)
P10.78922 (11)0.30280 (8)0.96424 (8)0.0320 (2)
O11.1158 (4)0.0601 (2)1.2518 (3)0.0502 (6)
O20.9867 (3)0.1202 (2)1.3543 (2)0.0395 (5)
O30.6973 (4)0.1392 (3)0.9854 (3)0.0498 (6)
O40.6226 (3)0.3665 (3)1.0706 (2)0.0451 (5)
O50.8309 (3)0.4285 (2)0.7834 (2)0.0387 (5)
C11.0559 (4)0.0885 (3)1.2283 (3)0.0290 (5)
C21.0610 (4)0.2351 (3)1.0582 (3)0.0362 (6)
H10.64690.55660.62760.033*
H12A0.82080.64520.36150.037*
H12B0.57890.68630.29150.037*
H13A0.73930.42620.31130.038*
H13B0.77240.35710.50390.038*
H14A0.71450.83240.49430.059*
H14B0.48950.80980.61490.059*
H14C0.47500.88040.42000.059*
H21.03140.04041.44180.059*0.50
H30.76850.11050.91670.075*
H40.55070.45501.00830.068*0.50
H2A1.17350.20660.98400.043*
H2B1.11120.32961.06480.043*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0289 (10)0.0274 (11)0.0255 (11)0.0009 (8)0.0057 (8)0.0119 (9)
C120.0299 (12)0.0338 (13)0.0256 (13)0.0024 (9)0.0007 (10)0.0123 (11)
C130.0276 (12)0.0366 (14)0.0324 (14)0.0003 (10)0.0000 (10)0.0188 (12)
C140.0458 (15)0.0306 (14)0.0445 (17)0.0016 (11)0.0062 (12)0.0203 (13)
P10.0334 (4)0.0353 (4)0.0255 (4)0.0042 (3)0.0059 (3)0.0138 (3)
O10.0761 (14)0.0373 (11)0.0358 (12)0.0146 (10)0.0150 (10)0.0185 (10)
O20.0507 (11)0.0394 (11)0.0291 (11)0.0081 (8)0.0089 (8)0.0184 (9)
O30.0570 (13)0.0497 (13)0.0494 (14)0.0117 (10)0.0077 (10)0.0255 (11)
O40.0456 (11)0.0523 (13)0.0313 (11)0.0176 (9)0.0035 (8)0.0204 (10)
O50.0393 (10)0.0405 (11)0.0256 (10)0.0086 (8)0.0075 (8)0.0088 (9)
C10.0236 (11)0.0321 (13)0.0372 (15)0.0059 (9)0.0100 (10)0.0212 (12)
C20.0350 (13)0.0372 (15)0.0307 (15)0.0015 (10)0.0027 (11)0.0126 (12)
Geometric parameters (Å, º) top
N1—C121.490 (3)O1—C11.252 (3)
N1—C13i1.492 (3)O2—C11.293 (3)
N1—C141.492 (3)C1—C21.473 (3)
N1—H10.91C2—P11.811 (2)
C12—C131.506 (3)P1—O31.562 (2)
C12—H12A0.97P1—O41.5168 (18)
C12—H12B0.97P1—O51.4874 (19)
C13—H13A0.97O2—H20.82
C13—H13B0.97O3—H30.82
C14—H14A0.96O4—H40.82
C14—H14B0.96C2—H2A0.97
C14—H14C0.96C2—H2B0.97
C12—N1—C13i110.22 (18)N1—C14—H14C109.5
C12—N1—C14111.22 (19)H14A—C14—H14C109.5
C13i—N1—C14112.07 (18)H14B—C14—H14C109.5
C12—N1—H1107.7O3—P1—O4106.38 (12)
C13i—N1—H1107.7O4—P1—O5115.41 (11)
C14—N1—H1107.7O5—P1—O3112.35 (11)
N1—C12—C13111.5 (2)O1—C1—C2122.2 (2)
N1—C12—H12A109.3O2—C1—C2116.8 (2)
C13—C12—H12A109.3O3—P1—C2106.20 (12)
N1—C12—H12B109.3O4—P1—C2107.96 (12)
C13—C12—H12B109.3O5—P1—C2108.09 (11)
H12A—C12—H12B108.0O1—C1—O2121.0 (2)
N1i—C13—C12110.43 (18)C1—C2—P1114.59 (18)
N1i—C13—H13A109.6C1—O2—H2109.5
C12—C13—H13A109.6P1—O3—H3109.5
N1i—C13—H13B109.6P1—O4—H4109.5
C12—C13—H13B109.6C1—C2—H2A108.6
H13A—C13—H13B108.1P1—C2—H2A108.6
N1—C14—H14A109.5C1—C2—H2B108.6
N1—C14—H14B109.5P1—C2—H2B108.6
H14A—C14—H14B109.5H2A—C2—H2B107.6
O3—P1—C2—C148.8 (2)O2—C1—C2—P183.6 (2)
O4—P1—C2—C164.9 (2)C13i—N1—C12—C1357.0 (3)
O5—P1—C2—C1169.60 (18)C14—N1—C12—C13178.06 (19)
O1—C1—C2—P196.6 (2)N1—C12—C13—N1i57.1 (3)
Symmetry code: (i) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O50.911.732.642 (2)176
O2—H2···O2ii0.821.722.494 (4)158
O3—H3···O1iii0.821.802.612 (3)171
O4—H4···O4iv0.821.662.465 (3)165
C12—H12A···O5v0.972.463.203 (3)133
Symmetry codes: (ii) x+2, y, z+3; (iii) x+2, y, z+2; (iv) x+1, y+1, z+2; (v) x+2, y+1, z+1.

Experimental details

Crystal data
Chemical formulaC6H16N22+·2C2H4O5P
Mr394.25
Crystal system, space groupTriclinic, P1
Temperature (K)293
a, b, c (Å)5.9217 (4), 8.9858 (5), 8.9987 (6)
α, β, γ (°)61.730 (3), 81.885 (3), 81.448 (4)
V3)415.65 (5)
Z1
Radiation typeMo Kα
µ (mm1)0.32
Crystal size (mm)0.34 × 0.20 × 0.06
Data collection
DiffractometerKappa-CCD
diffractometer
Absorption correctionMulti-scan
(DENZO-SMN; Otwinowski & Minor, 1997)
Tmin, Tmax0.900, 0.981
No. of measured, independent and
observed [I > 2σ(I)] reflections
5103, 1900, 1320
Rint0.045
(sin θ/λ)max1)0.652
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.045, 0.125, 1.04
No. of reflections1900
No. of parameters114
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.26, 0.39

Computer programs: Collect (Nonius, 1997-2000), DENZO-SMN (Otwinowski & Minor, 1997), DENZO-SMN, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 2001), SHELXL97 and PRPKAPPA (Ferguson, 1999).

Selected geometric parameters (Å, º) top
N1—C121.490 (3)C1—C21.473 (3)
N1—C13i1.492 (3)C2—P11.811 (2)
N1—C141.492 (3)P1—O31.562 (2)
C12—C131.506 (3)P1—O41.5168 (18)
O1—C11.252 (3)P1—O51.4874 (19)
O2—C11.293 (3)
O3—P1—O4106.38 (12)O3—P1—C2106.20 (12)
O4—P1—O5115.41 (11)O4—P1—C2107.96 (12)
O5—P1—O3112.35 (11)O5—P1—C2108.09 (11)
O1—C1—C2122.2 (2)O1—C1—O2121.0 (2)
O2—C1—C2116.8 (2)C1—C2—P1114.59 (18)
O3—P1—C2—C148.8 (2)O1—C1—C2—P196.6 (2)
O4—P1—C2—C164.9 (2)O2—C1—C2—P183.6 (2)
O5—P1—C2—C1169.60 (18)
Symmetry code: (i) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O50.911.732.642 (2)176
O2—H2···O2ii0.821.722.494 (4)158
O3—H3···O1iii0.821.802.612 (3)171
O4—H4···O4iv0.821.662.465 (3)165
C12—H12A···O5v0.972.463.203 (3)133
Symmetry codes: (ii) x+2, y, z+3; (iii) x+2, y, z+2; (iv) x+1, y+1, z+2; (v) x+2, y+1, z+1.
 

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