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The title compound, C6H8N+.C5H9O6P2, has been prepared via hydro­lysis of 3-methyl-1,2-buta­diene-1,1-di­phospho­nic tetrakis­(tri­methyl­silyl) ester, and stabilization of the di­phospho­nic acid thus formed as an anilinium salt. Both ions possess mirror symmetry, with all the C atoms of the anion and the N, ipso-C and para-C atoms of the cation being situated in the mirror plane. Adjacent anionic units form associations through cyclic dimeric {P(=O)(OH)}2 and chain-propagating P—OH...O=P interactions, with the anilinium ion being hydrogen bonded to three adjacent di­phospho­nate anions.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802005743/om6082sup1.cif
Contains datablocks global, 4

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536802005743/om60824sup2.hkl
Contains datablock 4

CCDC reference: 185774

Key indicators

  • Single-crystal X-ray study
  • T = 193 K
  • Mean [sigma](C-C) = 0.005 Å
  • R factor = 0.043
  • wR factor = 0.110
  • Data-to-parameter ratio = 11.4

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


Yellow Alert Alert Level C:
PLAT_728 Alert C D-H..A Calc 172(6), Rep 170.90, Dev. 1.10 Deg. O1 -H1 -O1 1.555 1.555 7.545 PLAT_748 Alert C D-H..A Calc 137.5(8), Rep 137.30 .... Missing s.u. N -H1A -O1 1.555 1.555 1.555
0 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
2 Alert Level C = Please check

Comment top

Diphosphonate compounds are of interest to us due to their known biological activity, particularly their ability to reduce tumour-induced bone resorption (Fleisch, 1998). Their affinity for bone and other calcified tissues (Wingen & Schmähl, 1985) has led others to demonstrate the utility of functionalized organic diphosphonates to facilitate site-preferential delivery of antiosteosarcomic agents (Klenner et al., 1990). Recently, we have studied the reactivity of polyfunctional electrophilic and nucleophilic reagents with 1,2-alkadiene mono- and diphosphonates. These compounds are relatively easy to prepare by acetylene–allene rearrangement of acetylene phosphines, which are obtained by the reaction of phosphorus trichloride (or chlorophosphines) with α-acetylenic alcohols under mild conditions to afford 1,2-alkadiene mono- and diphosphonates (Ignat'ev et al., 1967; Mark, 1969).

In this communication, we wish to describe the preparation of the previously unknown 3-methyl-1,2-butadiene-1,1-diphosphonic acid, (3), and its structural elucidation. We used 3-methyl-1,2-butadiene-1,1-diphosphonic tetraethyl ester, (1), as a convenient precursor for the synthesis of the acid (3) by a procedure recently developed in our laboratory (Angelov, 2002). By replacing the ethyl groups in (I) with trimethylsilyl groups, we were able to prepare 3-methyl-1,2-butadiene-1,1-diphosphonic tetrakis(trimethylsilyl) ester, (2). Hydrolysis of (2) [31P NMR (CDCl3), p.p.m.: δ (versus. ext. 85% H3PO4) -7.90] with methanol afforded the acid (3). Compound (3) [31P NMR (CDCl3), p.p.m.: δ(versus. ext. 85% H3PO4) 3.42] is a colorless hygroscopic powder which quickly absorbs moisture and becomes an oil. We stabilized (3) by treatment with one molar equivalent of aniline, and were able to prepare a stable anilinium salt (4).

In the solid-state structure of (4), both the Me2CC C{PO(OH)2}{PO2(OH)}- ion and the associated anilinium ion are situated upon a crystallographic mirror plane (0,y,z) (primed atoms are related to unprimed ones via this plane). As shown in Fig. 1, this mirror plane contains atoms C1–C5 of the anion and N/C6/C9 of the PhNH3+ ion. The allenic unit is essentially linear [C1—C2—C3 = 176.5 (4)°], with the C1—C2 [1.308 (5) Å] and C2—C3 [1.298 (5) Å] distances approximately equal. Despite the mirror plane, atom O1' is drawn without a hydroxylic H atom. This is due to a hydrogen-bonded interaction with an adjacent twofold-related molecule (see below).

Fig. 2 illustrates the interactions between adjacent anilinium and diphosphonate ions (the relevant hydrogen-bond parameters are given in Table 2). Adjacent diphosphonate ions form hydrogen-bonded interactions in two different manners. A chain interaction is observed between O1—H1 and the O1 atom (indicated as O1'') related by the (1/4,y,1/4) twofold axis, in which the O1—H1 and O1*···H1 distances are equal [1.209(3 Å], due to the location of H1 upon the twofold axis. A cyclic interaction is also formed about the inversion center (1/4,1/4,0) by O2—H2 and the inversion-generated O3 atom (indicated as O3*), with O3 being hydrogen bonded to O2*-H2*. As might be seen in Fig. 1, one of the ammonium H atoms of the anilinium ion is within 2.24 (4) Å of both O1 and O1', forming a cyclic C(—PO···)2H unit. A closer [1.87 (3) Å], more linear interaction is formed between the anilinium H1B atom and O3''.

Experimental top

3-Methyl-1,2-butadiene-1,1-diphosphonic acid, (3), was treated with aniline to yield the title compound (4). The crude salt, (4), was recrystallized from water to yield colorless crystals [m.p. 450 K; 31P NMR (D2O), p.p.m.: δ(versus. ext. 85% H3PO4) 9.64].

Refinement top

Data for compound (4) were collected at 193 K on a Bruker PLATFORM diffractometer equipped with SMART 1000 CCD area detector. The structure of (4) was solved through use of the direct-methods program SHELXS97 (Sheldrick, 1990). Except for H1, the H atoms were generated in idealized positions (according to the sp2 or sp3 geometries of their parent C, N or O atoms), and then allowed to refine with no restraints on coordinates or isotropic displacement parameters. The hydroxyl H1 atom was located from a difference Fourier map, and found to lie on the crystallographic twofold axis (1/4,y,1/4). It was also allowed to freely refine. Its Ueq value [0.10 (2) e Å-3] is significantly larger than that for its attached oxygen, but attempts to model it as belonging to a rotationally disordered O1—H1···O1'' unit (i.e. by initially inserting H1 between O1 and O1'' approximately 0.8 Å from O1, with an occupancy factor of 1/2, then allowing free refinement) yielded less satisfactory results [Ueq(H1) = 0.009 (15) e Å-3, O1—H1 = 0.72 (4) Å].

Computing details top

Data collection: SMART (Bruker, 1997); cell refinement: SMART; data reduction: SHELXTL (Sheldrick, 1997a); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997b); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2001).

Figures top
[Figure 1] Fig. 1. Perspective view of the Me2CCC{PO(OH)2}{PO2(OH)}- ion and the associated anilinium ion showing the atom-labelling scheme. Non-H atoms are represented by Gaussian ellipsoids at the 50% probability level. Primed atoms are related to unprimed ones via the crystallographic mirror plane (0,y,z).
[Figure 2] Fig. 2. View illustrating the hydrogen-bonded interactions between neighbouring anilinium and diphosphonate ions. Primed atoms are generated by the mirror plane (0,y,z), double-primed atoms by the twofold axis (1/4,y,1/4), and starred atoms by the inversion center (1/4,1/4 0). Methyl and phenyl H atoms have been omitted, as have C-atom displacement ellipsoids.
3-methyl-1,2-butadiene-1,1-diphosphonic acid, anilinium salt top
Crystal data top
C6H8N+·C5H9O6P2Dx = 1.447 Mg m3
Mr = 321.20Melting point: 450 K
Orthorhombic, CmcaMo Kα radiation, λ = 0.71073 Å
a = 9.9331 (14) ÅCell parameters from 2913 reflections
b = 20.188 (3) Åθ = 2.5–26.3°
c = 14.701 (2) ŵ = 0.32 mm1
V = 2947.9 (7) Å3T = 193 K
Z = 8Plate, colorless
F(000) = 13440.47 × 0.15 × 0.04 mm
Data collection top
Bruker PLATFORM
diffractometer/SMART 1000 CCD area-detector
1604 independent reflections
Radiation source: fine-focus sealed tube1177 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.065
Detector resolution: 8.192 pixels mm-1θmax = 26.4°, θmin = 2.0°
ω scansh = 1112
Absorption correction: empirical (using intensity measurements)
(SADABS; Sheldrick, 1996)
k = 2425
Tmin = 0.865, Tmax = 0.987l = 1618
7136 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)] = 0.043Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.110All H-atom parameters refined
S = 1.02 w = 1/[σ2(Fo2) + (0.0514P)2 + 4.4604P]
where P = (Fo2 + 2Fc2)/3
1604 reflections(Δ/σ)max < 0.001
141 parametersΔρmax = 0.56 e Å3
0 restraintsΔρmin = 0.36 e Å3
Crystal data top
C6H8N+·C5H9O6P2V = 2947.9 (7) Å3
Mr = 321.20Z = 8
Orthorhombic, CmcaMo Kα radiation
a = 9.9331 (14) ŵ = 0.32 mm1
b = 20.188 (3) ÅT = 193 K
c = 14.701 (2) Å0.47 × 0.15 × 0.04 mm
Data collection top
Bruker PLATFORM
diffractometer/SMART 1000 CCD area-detector
1604 independent reflections
Absorption correction: empirical (using intensity measurements)
(SADABS; Sheldrick, 1996)
1177 reflections with I > 2σ(I)
Tmin = 0.865, Tmax = 0.987Rint = 0.065
7136 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0430 restraints
wR(F2) = 0.110All H-atom parameters refined
S = 1.02Δρmax = 0.56 e Å3
1604 reflectionsΔρmin = 0.36 e Å3
141 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.

Hydrogen atoms were refined with fixed C—H, N—H or O—H distances and with isotropici displacement parameters 20% (for C—H or N—H) or 50% (for O—H) greater than those for their attached atoms. The close contact (2.414 (3) Å) between O1 and the symmetry-related O1 at (1/2 - x, y, 1/2 - z) suggested a hydrogen-bonded interaction between these atoms, thus the hydroxylic hydrogen H1 was assigned an occupancy factor of 0.5 to allow for the disorder generated by the intervening twofold axis (1/4, y, 1/4).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
P0.15793 (6)0.20007 (3)0.10477 (4)0.0176 (2)
O10.15184 (17)0.17459 (9)0.20181 (12)0.0258 (4)
H10.25000.179 (3)0.25000.10 (2)*
O20.16508 (19)0.27709 (9)0.10995 (14)0.0235 (4)
H20.188 (3)0.2919 (15)0.063 (2)0.039 (10)*
O30.27166 (16)0.17290 (8)0.04932 (11)0.0209 (4)
C10.00000.17891 (17)0.0529 (2)0.0172 (7)
C20.00000.15157 (18)0.0279 (2)0.0225 (8)
C30.00000.1281 (2)0.1100 (3)0.0280 (9)
C40.00000.1753 (3)0.1889 (3)0.0415 (12)
H4A0.00000.223 (2)0.166 (3)0.048 (14)*
H4B0.073 (3)0.1669 (15)0.226 (2)0.056 (11)*
C50.00000.0550 (3)0.1293 (4)0.0420 (12)
H5A0.00000.029 (3)0.081 (4)0.062 (17)*
H5B0.072 (4)0.0443 (17)0.165 (2)0.063 (12)*
N0.00000.12706 (16)0.3615 (2)0.0193 (7)
H1A0.00000.141 (2)0.305 (3)0.043 (13)*
H1B0.074 (3)0.1439 (14)0.3899 (19)0.031 (8)*
C60.00000.05491 (17)0.3675 (2)0.0186 (7)
C70.1184 (3)0.02160 (16)0.3720 (3)0.0483 (10)
H70.199 (4)0.044 (2)0.366 (3)0.083 (13)*
C80.1170 (4)0.04641 (16)0.3820 (3)0.0531 (11)
H80.194 (4)0.0686 (18)0.382 (3)0.073 (12)*
C90.00000.0805 (2)0.3867 (3)0.0303 (9)
H90.00000.128 (2)0.394 (3)0.025 (10)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
P0.0130 (3)0.0249 (4)0.0149 (3)0.0002 (3)0.0002 (2)0.0018 (3)
O10.0182 (9)0.0427 (11)0.0167 (9)0.0046 (8)0.0032 (7)0.0079 (8)
O20.0212 (9)0.0275 (11)0.0218 (10)0.0018 (8)0.0054 (8)0.0033 (8)
O30.0162 (8)0.0261 (10)0.0205 (9)0.0035 (7)0.0025 (7)0.0019 (7)
C10.0144 (16)0.0226 (19)0.0146 (17)0.0000.0000.0029 (14)
C20.0172 (17)0.027 (2)0.024 (2)0.0000.0000.0018 (16)
C30.0254 (19)0.039 (2)0.0196 (19)0.0000.0000.0037 (17)
C40.050 (3)0.056 (3)0.019 (2)0.0000.0000.001 (2)
C50.051 (3)0.039 (3)0.035 (3)0.0000.0000.010 (2)
N0.0157 (15)0.0236 (18)0.0187 (16)0.0000.0000.0021 (13)
C60.0205 (17)0.0195 (19)0.0159 (17)0.0000.0000.0020 (14)
C70.0200 (15)0.0275 (18)0.097 (3)0.0013 (12)0.0071 (16)0.0009 (18)
C80.0305 (17)0.0238 (17)0.105 (3)0.0069 (14)0.0134 (19)0.0009 (19)
C90.040 (2)0.021 (2)0.030 (2)0.0000.0000.0028 (17)
Geometric parameters (Å, º) top
P—O11.5177 (18)C5—H5A0.88 (5)
P—O21.558 (2)C5—H5B0.91 (3)
P—O31.4972 (17)N—C61.459 (5)
P—C11.7959 (18)N—H1A0.88 (5)
O1—H11.209 (5)N—H1B0.91 (3)
O2—H20.78 (3)C6—C71.356 (3)
C1—C21.309 (5)C6—C7i1.356 (3)
C2—C31.296 (5)C7—C81.381 (5)
C3—C41.501 (6)C7—H70.92 (4)
C3—C51.504 (6)C8—C91.352 (4)
C4—H4A1.03 (5)C8—H80.89 (4)
C4—H4B0.93 (3)C9—H90.96 (4)
O1—P—O2107.10 (11)C3—C5—H5A116 (3)
O1—P—O3114.69 (10)C3—C5—H5B110 (2)
O1—P—C1106.49 (12)H5A—C5—H5B109 (3)
O2—P—O3110.96 (10)C6—N—H1A113 (3)
O2—P—C1107.33 (13)C6—N—H1B110.1 (18)
O3—P—C1109.92 (12)H1A—N—H1B108 (2)
P—O1—H1119.5 (12)C7—C6—C7i120.2 (4)
P—O2—H2111 (2)N—C6—C7119.87 (19)
P—C1—Pi121.74 (19)C6—C7—C8119.3 (3)
P—C1—C2119.04 (10)C6—C7—H7120 (3)
C1—C2—C3176.5 (4)C8—C7—H7120 (3)
C2—C3—C4119.2 (4)C7—C8—C9121.3 (3)
C2—C3—C5122.3 (4)C7—C8—H8120 (2)
C4—C3—C5118.5 (4)C9—C8—H8119 (2)
C3—C4—H4A110 (3)C8—C9—C8i118.5 (4)
C3—C4—H4B110 (2)C8—C9—H9120.7 (2)
H4A—C4—H4B112 (2)
O1—P—C1—Pi51.9 (2)O3—P—C1—C28.2 (3)
O1—P—C1—C2133.0 (3)N—C6—C7—C8176.9 (4)
O2—P—C1—Pi62.5 (2)C7i—C6—C7—C80.5 (7)
O2—P—C1—C2112.6 (3)C6—C7—C8—C90.4 (6)
O3—P—C1—Pi176.72 (16)C7—C8—C9—C8i0.3 (8)
Symmetry code: (i) x, y, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O1ii1.21 (1)1.21 (1)2.411 (3)171
O2—H2···O3iii0.78 (3)1.85 (3)2.626 (3)175.6
N—H1A···O10.88 (5)2.24 (4)2.951 (3)137
N—H1A···O1i0.88 (5)2.24 (4)2.951 (3)137
N—H1B···O3ii0.91 (3)1.87 (3)2.778 (3)176.4
Symmetry codes: (i) x, y, z; (ii) x+1/2, y, z+1/2; (iii) x+1/2, y+1/2, z.

Experimental details

Crystal data
Chemical formulaC6H8N+·C5H9O6P2
Mr321.20
Crystal system, space groupOrthorhombic, Cmca
Temperature (K)193
a, b, c (Å)9.9331 (14), 20.188 (3), 14.701 (2)
V3)2947.9 (7)
Z8
Radiation typeMo Kα
µ (mm1)0.32
Crystal size (mm)0.47 × 0.15 × 0.04
Data collection
DiffractometerBruker PLATFORM
diffractometer/SMART 1000 CCD area-detector
Absorption correctionEmpirical (using intensity measurements)
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.865, 0.987
No. of measured, independent and
observed [I > 2σ(I)] reflections
7136, 1604, 1177
Rint0.065
(sin θ/λ)max1)0.626
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.043, 0.110, 1.02
No. of reflections1604
No. of parameters141
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.56, 0.36

Computer programs: SMART (Bruker, 1997), SMART, SHELXTL (Sheldrick, 1997a), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997b), SHELXTL and PLATON (Spek, 2001).

Selected geometric parameters (Å, º) top
P—O11.5177 (18)C3—C51.504 (6)
P—O21.558 (2)N—C61.459 (5)
P—O31.4972 (17)N—H1A0.88 (5)
P—C11.7959 (18)N—H1B0.91 (3)
O1—H11.209 (5)C6—C71.356 (3)
O2—H20.78 (3)C6—C7i1.356 (3)
C1—C21.309 (5)C7—C81.381 (5)
C2—C31.296 (5)C8—C91.352 (4)
C3—C41.501 (6)
O1—P—O2107.10 (11)C2—C3—C4119.2 (4)
O1—P—O3114.69 (10)C2—C3—C5122.3 (4)
O1—P—C1106.49 (12)C4—C3—C5118.5 (4)
O2—P—O3110.96 (10)C6—N—H1A113 (3)
O2—P—C1107.33 (13)C6—N—H1B110.1 (18)
O3—P—C1109.92 (12)H1A—N—H1B108 (2)
P—O1—H1119.5 (12)C7—C6—C7i120.2 (4)
P—O2—H2111 (2)N—C6—C7119.87 (19)
P—C1—Pi121.74 (19)C6—C7—C8119.3 (3)
P—C1—C2119.04 (10)C7—C8—C9121.3 (3)
C1—C2—C3176.5 (4)C8—C9—C8i118.5 (4)
Symmetry code: (i) x, y, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O1ii1.209 (3)1.209 (3)2.411 (3)170.9
O2—H2···O3iii0.78 (3)1.85 (3)2.626 (3)175.6
N—H1A···O10.88 (5)2.24 (4)2.951 (3)137.3
N—H1A···O1i0.88 (5)2.24 (4)2.951 (3)137.3
N—H1B···O3ii0.91 (3)1.87 (3)2.778 (3)176.4
Symmetry codes: (i) x, y, z; (ii) x+1/2, y, z+1/2; (iii) x+1/2, y+1/2, z.
 

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