Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103023710/sk1672sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270103023710/sk1672Isup2.hkl |
CCDC reference: 229092
A sample of the title compound was donated by Dr Lize Binderup (LEO Pharmaceutical Products, Copenhagen, Denmark; LEO code name SL 2333). Crystals of (I) suitable for X-ray diffraction were obtained by slow evaporation of a water solution in an oven at 315 K.
H atoms attached to O and N atoms had their positional parameters freely refined, while those H atoms attached to C atoms were treated as riding. All H atoms had their displacement parameters constrained to 1.2 (for those bonded to C atoms) or 1.5 (for those bonded to O and N atoms) times that of their hosts. O—H distances were refined with a restrained bond distance of 0.85 (3) Å using the DFIX command implemented in SHELXL97 (Sheldrick, 1997).
Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1993); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: MSC/AFC Diffractometer Control Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ZORTEP (Zsolnai & Pritzkow, 1995); software used to prepare material for publication: Cambridge Structural Database (Version?; Allen, 2002), PLATON (Spek, 2003) and WinGX (Farrugia, 1999).
C8H19NO7P2 | F(000) = 640 |
Mr = 303.18 | Dx = 1.631 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71069 Å |
Hall symbol: -P 2ybc | Cell parameters from 20 reflections |
a = 10.590 (4) Å | θ = 4–12.5° |
b = 11.490 (3) Å | µ = 0.38 mm−1 |
c = 11.344 (5) Å | T = 293 K |
β = 116.58 (3)° | Block, colourless |
V = 1234.4 (8) Å3 | 0.45 × 0.35 × 0.30 mm |
Z = 4 |
Rigaku AFC-6S diffractometer | Rint = 0.033 |
Graphite monochromator | θmax = 25.0°, θmin = 2.2° |
ω/2θ scans | h = −12→7 |
Absorption correction: ψ scan (MSC/AFC Diffractometer Control Software; Molecular Structure Corporation, 1993) | k = −13→13 |
Tmin = 0.786, Tmax = 0.893 | l = −13→13 |
5614 measured reflections | 3 standard reflections every 400 reflections |
2184 independent reflections | intensity decay: 4.9% |
1938 reflections with I > 2σ(I) |
Refinement on F2 | H atoms treated by a mixture of independent and constrained refinement |
Least-squares matrix: full | w = 1/[σ2(Fo2) + (0.0479P)2 + 0.8012P] where P = (Fo2 + 2Fc2)/3 |
R[F2 > 2σ(F2)] = 0.034 | (Δ/σ)max = 0.007 |
wR(F2) = 0.092 | Δρmax = 0.37 e Å−3 |
S = 1.04 | Δρmin = −0.31 e Å−3 |
2184 reflections | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
179 parameters | Extinction coefficient: 0.0279 (19) |
4 restraints |
C8H19NO7P2 | V = 1234.4 (8) Å3 |
Mr = 303.18 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 10.590 (4) Å | µ = 0.38 mm−1 |
b = 11.490 (3) Å | T = 293 K |
c = 11.344 (5) Å | 0.45 × 0.35 × 0.30 mm |
β = 116.58 (3)° |
Rigaku AFC-6S diffractometer | 1938 reflections with I > 2σ(I) |
Absorption correction: ψ scan (MSC/AFC Diffractometer Control Software; Molecular Structure Corporation, 1993) | Rint = 0.033 |
Tmin = 0.786, Tmax = 0.893 | 3 standard reflections every 400 reflections |
5614 measured reflections | intensity decay: 4.9% |
2184 independent reflections |
R[F2 > 2σ(F2)] = 0.034 | 4 restraints |
wR(F2) = 0.092 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | Δρmax = 0.37 e Å−3 |
2184 reflections | Δρmin = −0.31 e Å−3 |
179 parameters |
Experimental. 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 > 2sigma(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. |
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. |
x | y | z | Uiso*/Ueq | ||
P1 | 0.34095 (5) | 0.62923 (4) | 0.76830 (5) | 0.01868 (18) | |
P2 | 0.59139 (5) | 0.46089 (4) | 0.85410 (5) | 0.01914 (18) | |
O1 | 0.25295 (15) | 0.71026 (12) | 0.65419 (14) | 0.0251 (3) | |
O2 | 0.43333 (16) | 0.70918 (12) | 0.88656 (14) | 0.0252 (3) | |
H2 | 0.453 (3) | 0.681 (2) | 0.960 (2) | 0.038* | |
O3 | 0.25735 (15) | 0.54041 (12) | 0.80024 (14) | 0.0249 (3) | |
O4 | 0.66687 (16) | 0.54469 (12) | 0.97226 (14) | 0.0275 (4) | |
H4 | 0.687 (3) | 0.517 (2) | 1.051 (2) | 0.041* | |
O5 | 0.51602 (15) | 0.36261 (11) | 0.88410 (13) | 0.0228 (3) | |
O6 | 0.69586 (15) | 0.41966 (12) | 0.80360 (15) | 0.0250 (3) | |
H6 | 0.716 (3) | 0.3491 (19) | 0.825 (3) | 0.038* | |
O7 | 0.54304 (15) | 0.62913 (12) | 0.68036 (15) | 0.0258 (3) | |
H7 | 0.511 (3) | 0.694 (2) | 0.668 (3) | 0.039* | |
N1 | 0.21341 (18) | 0.42888 (14) | 0.36797 (16) | 0.0213 (4) | |
H1 | 0.280 (3) | 0.424 (2) | 0.340 (2) | 0.032* | |
C1 | 0.4615 (2) | 0.55028 (16) | 0.71820 (19) | 0.0189 (4) | |
C2 | 0.3827 (2) | 0.46262 (17) | 0.6055 (2) | 0.0237 (5) | |
H8 | 0.4506 | 0.4278 | 0.5804 | 0.028* | |
H9 | 0.3456 | 0.4008 | 0.6393 | 0.028* | |
C3 | 0.2620 (2) | 0.51223 (17) | 0.4825 (2) | 0.0251 (5) | |
H10 | 0.1834 | 0.5301 | 0.5014 | 0.030* | |
H11 | 0.2924 | 0.5843 | 0.4585 | 0.030* | |
C4 | 0.0790 (2) | 0.47317 (18) | 0.2564 (2) | 0.0255 (5) | |
H12 | 0.0940 | 0.5518 | 0.2341 | 0.031* | |
H13 | 0.0052 | 0.4757 | 0.2848 | 0.031* | |
C5 | 0.0318 (2) | 0.3966 (2) | 0.1354 (2) | 0.0331 (5) | |
H14 | 0.1024 | 0.3982 | 0.1030 | 0.040* | |
H15 | −0.0559 | 0.4263 | 0.0665 | 0.040* | |
C6 | 0.0104 (2) | 0.27177 (19) | 0.1682 (2) | 0.0347 (5) | |
H16 | −0.0670 | 0.2687 | 0.1917 | 0.042* | |
H17 | −0.0132 | 0.2225 | 0.0917 | 0.042* | |
C7 | 0.1445 (3) | 0.2280 (2) | 0.2821 (2) | 0.0390 (6) | |
H18 | 0.1283 | 0.1502 | 0.3058 | 0.047* | |
H19 | 0.2188 | 0.2232 | 0.2545 | 0.047* | |
C8 | 0.1924 (2) | 0.30618 (17) | 0.4019 (2) | 0.0314 (5) | |
H20 | 0.1223 | 0.3054 | 0.4349 | 0.038* | |
H21 | 0.2804 | 0.2769 | 0.4709 | 0.038* |
U11 | U22 | U33 | U12 | U13 | U23 | |
P1 | 0.0203 (3) | 0.0141 (3) | 0.0217 (3) | −0.00102 (18) | 0.0095 (2) | −0.00047 (18) |
P2 | 0.0206 (3) | 0.0139 (3) | 0.0213 (3) | −0.00095 (18) | 0.0079 (2) | 0.00022 (18) |
O1 | 0.0268 (8) | 0.0188 (7) | 0.0252 (7) | 0.0007 (6) | 0.0076 (6) | 0.0010 (5) |
O2 | 0.0312 (8) | 0.0195 (7) | 0.0235 (7) | −0.0040 (6) | 0.0111 (7) | −0.0024 (6) |
O3 | 0.0230 (7) | 0.0221 (7) | 0.0295 (8) | −0.0038 (6) | 0.0116 (6) | 0.0009 (6) |
O4 | 0.0346 (8) | 0.0201 (7) | 0.0224 (7) | −0.0049 (6) | 0.0079 (7) | −0.0014 (6) |
O5 | 0.0261 (7) | 0.0177 (7) | 0.0248 (7) | −0.0022 (6) | 0.0117 (6) | 0.0009 (5) |
O6 | 0.0253 (8) | 0.0163 (7) | 0.0361 (8) | 0.0017 (6) | 0.0161 (7) | 0.0026 (6) |
O7 | 0.0287 (8) | 0.0165 (7) | 0.0388 (8) | 0.0026 (6) | 0.0208 (7) | 0.0070 (6) |
N1 | 0.0183 (9) | 0.0198 (8) | 0.0234 (9) | 0.0008 (7) | 0.0071 (7) | −0.0016 (7) |
C1 | 0.0215 (10) | 0.0158 (9) | 0.0200 (9) | −0.0010 (7) | 0.0099 (8) | 0.0003 (7) |
C2 | 0.0271 (11) | 0.0185 (10) | 0.0227 (10) | 0.0010 (8) | 0.0085 (9) | −0.0032 (8) |
C3 | 0.0274 (11) | 0.0194 (9) | 0.0252 (10) | 0.0024 (8) | 0.0088 (9) | −0.0038 (8) |
C4 | 0.0206 (10) | 0.0232 (10) | 0.0267 (10) | 0.0025 (8) | 0.0053 (9) | 0.0035 (8) |
C5 | 0.0284 (12) | 0.0383 (12) | 0.0252 (11) | −0.0049 (10) | 0.0054 (9) | −0.0010 (9) |
C6 | 0.0279 (11) | 0.0307 (12) | 0.0355 (12) | −0.0061 (9) | 0.0053 (10) | −0.0085 (10) |
C7 | 0.0308 (12) | 0.0252 (11) | 0.0457 (14) | 0.0011 (10) | 0.0032 (11) | −0.0101 (10) |
C8 | 0.0325 (12) | 0.0182 (10) | 0.0331 (11) | 0.0007 (9) | 0.0054 (10) | 0.0011 (9) |
P1—O1 | 1.5269 (15) | C2—H8 | 0.9700 |
P1—O2 | 1.5576 (15) | C2—H9 | 0.9700 |
P1—O3 | 1.4979 (15) | C3—H10 | 0.9700 |
P1—C1 | 1.850 (2) | C3—H11 | 0.9700 |
P2—O4 | 1.5504 (15) | C4—C5 | 1.515 (3) |
P2—O5 | 1.5071 (14) | C4—H12 | 0.9700 |
P2—O6 | 1.5309 (16) | C4—H13 | 0.9700 |
P2—C1 | 1.851 (2) | C5—C6 | 1.524 (3) |
O2—H2 | 0.83 (2) | C5—H14 | 0.9700 |
O4—H4 | 0.88 (2) | C5—H15 | 0.9700 |
O6—H6 | 0.85 (2) | C6—C7 | 1.516 (3) |
O7—C1 | 1.443 (2) | C6—H16 | 0.9700 |
O7—H7 | 0.81 (2) | C6—H17 | 0.9700 |
N1—C8 | 1.504 (3) | C7—C8 | 1.514 (3) |
N1—C3 | 1.507 (3) | C7—H18 | 0.9700 |
N1—C4 | 1.508 (3) | C7—H19 | 0.9700 |
N1—H1 | 0.90 (3) | C8—H20 | 0.9700 |
C1—C2 | 1.546 (3) | C8—H21 | 0.9700 |
C2—C3 | 1.520 (3) | ||
O1—P1—O2 | 106.28 (8) | N1—C3—H10 | 109.2 |
O1—P1—O3 | 114.70 (9) | C2—C3—H10 | 109.2 |
O2—P1—O3 | 113.89 (9) | N1—C3—H11 | 109.2 |
O1—P1—C1 | 106.36 (9) | C2—C3—H11 | 109.2 |
O2—P1—C1 | 107.46 (9) | H10—C3—H11 | 107.9 |
O3—P1—C1 | 107.69 (9) | N1—C4—C5 | 111.68 (17) |
O4—P2—O5 | 112.98 (9) | N1—C4—H12 | 109.3 |
O4—P2—O6 | 109.65 (9) | C5—C4—H12 | 109.3 |
O5—P2—O6 | 113.39 (8) | N1—C4—H13 | 109.3 |
O4—P2—C1 | 106.20 (9) | C5—C4—H13 | 109.3 |
O5—P2—C1 | 109.41 (9) | H12—C4—H13 | 107.9 |
O6—P2—C1 | 104.62 (9) | C4—C5—C6 | 110.50 (18) |
P1—O2—H2 | 114.4 (19) | C4—C5—H14 | 109.6 |
P2—O4—H4 | 116.9 (18) | C6—C5—H14 | 109.6 |
P2—O6—H6 | 108.9 (18) | C4—C5—H15 | 109.6 |
C1—O7—H7 | 112 (2) | C6—C5—H15 | 109.6 |
C3—N1—C4 | 109.81 (15) | H14—C5—H15 | 108.1 |
C3—N1—C8 | 114.08 (16) | C7—C6—C5 | 109.64 (19) |
C4—N1—C8 | 109.82 (16) | C7—C6—H16 | 109.7 |
C8—N1—H1 | 105.1 (17) | C5—C6—H16 | 109.7 |
C3—N1—H1 | 109.2 (16) | C7—C6—H17 | 109.7 |
C4—N1—H1 | 108.6 (16) | C5—C6—H17 | 109.7 |
O7—C1—C2 | 109.66 (16) | H16—C6—H17 | 108.2 |
O7—C1—P1 | 111.75 (13) | C8—C7—C6 | 112.22 (19) |
C2—C1—P1 | 112.48 (14) | C8—C7—H18 | 109.2 |
O7—C1—P2 | 105.97 (13) | C6—C7—H18 | 109.2 |
C2—C1—P2 | 104.60 (13) | C8—C7—H19 | 109.2 |
P1—C1—P2 | 111.96 (10) | C6—C7—H19 | 109.2 |
C1—C2—C3 | 115.84 (16) | H18—C7—H19 | 107.9 |
C3—C2—H8 | 108.3 | N1—C8—C7 | 110.84 (19) |
C1—C2—H8 | 108.3 | N1—C8—H20 | 109.5 |
C3—C2—H9 | 108.3 | C7—C8—H20 | 109.5 |
C1—C2—H9 | 108.3 | N1—C8—H21 | 109.5 |
H8—C2—H9 | 107.4 | C7—C8—H21 | 109.5 |
N1—C3—C2 | 112.07 (16) | H20—C8—H21 | 108.1 |
O3—P1—C1—O7 | 177.75 (12) | O5—P2—C1—P1 | 67.55 (11) |
O1—P1—C1—O7 | 54.32 (14) | O6—P2—C1—P1 | −170.65 (9) |
O2—P1—C1—O7 | −59.17 (14) | O7—C1—C2—C3 | −70.3 (2) |
O3—P1—C1—C2 | 53.90 (15) | P1—C1—C2—C3 | 54.7 (2) |
O1—P1—C1—C2 | −69.52 (15) | P2—C1—C2—C3 | 176.44 (16) |
O2—P1—C1—C2 | 176.98 (13) | C8—N1—C3—C2 | 46.7 (2) |
O1—P1—C1—P2 | 173.02 (9) | C4—N1—C3—C2 | 170.49 (18) |
O2—P1—C1—P2 | 59.53 (12) | C1—C2—C3—N1 | 167.02 (16) |
O3—P1—C1—P2 | −63.55 (12) | C8—N1—C4—C5 | −57.9 (2) |
O5—P2—C1—O7 | −170.38 (11) | C3—N1—C4—C5 | 175.89 (17) |
O6—P2—C1—O7 | −48.58 (14) | N1—C4—C5—C6 | 57.8 (3) |
O4—P2—C1—O7 | 67.38 (14) | C4—C5—C6—C7 | −55.4 (3) |
O5—P2—C1—C2 | −54.53 (15) | C5—C6—C7—C8 | 55.5 (3) |
O6—P2—C1—C2 | 67.27 (14) | C3—N1—C8—C7 | −179.71 (18) |
O4—P2—C1—C2 | −176.77 (13) | C4—N1—C8—C7 | 56.5 (2) |
O4—P2—C1—P1 | −54.69 (12) | C6—C7—C8—N1 | −56.7 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2···O5i | 0.83 (2) | 1.72 (2) | 2.547 (2) | 172 (3) |
O4—H4···O3i | 0.88 (2) | 1.66 (2) | 2.531 (2) | 173 (3) |
O6—H6···O1ii | 0.85 (2) | 1.62 (2) | 2.466 (2) | 172 (3) |
O7—H7···O5iii | 0.81 (2) | 2.01 (2) | 2.777 (2) | 160 (3) |
N1—H1···O7iv | 0.90 (3) | 2.08 (3) | 2.943 (3) | 162 (2) |
N1—H1···O6iv | 0.90 (3) | 2.51 (3) | 3.068 (2) | 121 (2) |
Symmetry codes: (i) −x+1, −y+1, −z+2; (ii) −x+1, y−1/2, −z+3/2; (iii) −x+1, y+1/2, −z+3/2; (iv) −x+1, −y+1, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C8H19NO7P2 |
Mr | 303.18 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 293 |
a, b, c (Å) | 10.590 (4), 11.490 (3), 11.344 (5) |
β (°) | 116.58 (3) |
V (Å3) | 1234.4 (8) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.38 |
Crystal size (mm) | 0.45 × 0.35 × 0.30 |
Data collection | |
Diffractometer | Rigaku AFC-6S diffractometer |
Absorption correction | ψ scan (MSC/AFC Diffractometer Control Software; Molecular Structure Corporation, 1993) |
Tmin, Tmax | 0.786, 0.893 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5614, 2184, 1938 |
Rint | 0.033 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.034, 0.092, 1.04 |
No. of reflections | 2184 |
No. of parameters | 179 |
No. of restraints | 4 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.37, −0.31 |
Computer programs: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1993), MSC/AFC Diffractometer Control Software, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ZORTEP (Zsolnai & Pritzkow, 1995), Cambridge Structural Database (Version?; Allen, 2002), PLATON (Spek, 2003) and WinGX (Farrugia, 1999).
P1—O1 | 1.5269 (15) | P2—O6 | 1.5309 (16) |
P1—O2 | 1.5576 (15) | P2—C1 | 1.851 (2) |
P1—O3 | 1.4979 (15) | N1—C8 | 1.504 (3) |
P1—C1 | 1.850 (2) | N1—C3 | 1.507 (3) |
P2—O4 | 1.5504 (15) | N1—C4 | 1.508 (3) |
P2—O5 | 1.5071 (14) | ||
O1—P1—O2 | 106.28 (8) | O5—P2—O6 | 113.39 (8) |
O1—P1—O3 | 114.70 (9) | O4—P2—C1 | 106.20 (9) |
O2—P1—O3 | 113.89 (9) | O5—P2—C1 | 109.41 (9) |
O1—P1—C1 | 106.36 (9) | O6—P2—C1 | 104.62 (9) |
O2—P1—C1 | 107.46 (9) | C3—N1—C4 | 109.81 (15) |
O3—P1—C1 | 107.69 (9) | C3—N1—C8 | 114.08 (16) |
O4—P2—O5 | 112.98 (9) | C4—N1—C8 | 109.82 (16) |
O4—P2—O6 | 109.65 (9) | P1—C1—P2 | 111.96 (10) |
O1—P1—C1—P2 | 173.02 (9) | O4—P2—C1—P1 | −54.69 (12) |
O2—P1—C1—P2 | 59.53 (12) | O5—P2—C1—P1 | 67.55 (11) |
O3—P1—C1—P2 | −63.55 (12) | O6—P2—C1—P1 | −170.65 (9) |
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2···O5i | 0.83 (2) | 1.72 (2) | 2.547 (2) | 172 (3) |
O4—H4···O3i | 0.88 (2) | 1.66 (2) | 2.531 (2) | 173 (3) |
O6—H6···O1ii | 0.85 (2) | 1.62 (2) | 2.466 (2) | 172 (3) |
O7—H7···O5iii | 0.81 (2) | 2.01 (2) | 2.777 (2) | 160 (3) |
N1—H1···O7iv | 0.90 (3) | 2.08 (3) | 2.943 (3) | 162 (2) |
N1—H1···O6iv | 0.90 (3) | 2.51 (3) | 3.068 (2) | 121 (2) |
Symmetry codes: (i) −x+1, −y+1, −z+2; (ii) −x+1, y−1/2, −z+3/2; (iii) −x+1, y+1/2, −z+3/2; (iv) −x+1, −y+1, −z+1. |
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Bisphosphonates are important bone-remodelling mediators, commonly used as antiresorptive agents. In this context, they are indicated for the treatment of osteoporosis, hypercalcaemia and osteolytic metastases (Compston, 1994; Martin & Grill, 2000). Compounds of this class have proved their usefulness in a wide range of applications, such as herbicides (Chuiko et al., 1999; Gordon-Weeks et al., 1999), antiparasitics (Docampo, 2001; Martin et al., 2001), cholesterol-lowering agents (Hiyoshi et al., 2000; Niesor et al., 2001), drugs for the treatment of manic-depressive disorders (Atack et al., 1993; Fauroux & Freeman, 1999), anti-inflammatories and anti-arthritics (Schlachter et al., 1998), and heavy-metal decorporating agents (Fukuda et al., 1999). As is observed for several N-containing bisphosphonates, PHPBP is a potent antiresorptive agent, with a potency comparable with that of the commonly used medications alendronate, olpadronate and pamidronate (Widler et al., 2002). The results from another study demonstrated that PHPBP was as potent as related amine-bisphosphonates when tested as cholesterol-lowering agents (Amin et al., 1992).
Our interest in studying PHPBP, (I), by single-crystal X-ray crystallography arose from our previous observations concerning the conformation of the alkylamino backbone (Vega et al., 2002; Fernández & Vega, 2003). Thus, the structural determination of (I) has been carried out and the results of the work are presented here. \sch
Compound (I) (Figure 1) is a zwitterion: phosphonic atom O1 is ionized, and the H atom is transferred to atom N1, which adopts a tetrahedral geometry (Table 1). This behaviour is not an uncommon feature of amine-bisphosphonates, as has been observed previously for related compounds (Vega et al., 2002; Van Brussel et al., 2003; Fernández & Vega, 2003). The geometry of atoms P1 and P2 is tetrahedral, and is defined by atoms O1, O2 and O3, and O4, O5 and O6, respectively. In the former group, O—P—O and O—P—C bond angles range from 106.28 (8) to 114.70 (9)°, while for the second group, the values lie between 104.62 (9) and 113.39 (8)°. The largest angle is O1—P1—O3, which is formed by the pair of unprotonated atoms O1 and O3. P—O bond distances (Table 1) are close to 1.50 Å for P═O bonds (P1═O3 and P2═O5), and approximately 1.55 Å for protonated atoms (P1—O2 and P2—O4). With respect to these values, the P1—O1 and P2—O6 bond distances are intermediate, suggesting that the order of the bond lies between single and double. An explanation for this fact can be found when considering the intermolecular interactions in which these atoms are involved, as they form a hydrogen bond (Table 2).
The P—C bond distances in (I) are in good agreement with those of related compounds. In addition, the P—C—P bond angle (Table 1) has a value well within the range observed for other bisphosphonates containing the C—C—C—N chain (109.91–114.23°; Fernández & Vega, 2003). The sp3-hybridized atom C2 has a distorted tetrahedral geometry, as indicated by the value of 115.84 (16)° for the C1—C2—C3 bond angle. This fact could be attributed to a repulsive interaction between atoms C2 and C3 and some of the phosphonyl O atoms, namely C2—H9···O5 [D···A 3.051 (3) Å, H···A 2.58 Å and D—H···A 110°] and C3—H10···O1 [D···A 3.019 (3) Å, H···A 2.59 Å and D—H···A 108°].
The conformation of the C—C—C—N chain is close to trans, the C1—C2—C3—N1 torsion angle being 167.02 (16)°. Such a conformation is commonly found in related amine-bisphosphonates, e.g. in 1-hydroxy-3-(1-pyrrolidinyl)propylidene-1,1-bisphosphonic acid (EB 1053; Fernández & Vega, 2003). In spite of the molecular resemblance between (I) and this pyrrolidinyl bisphosphonate, the C2—C3 bond is disposed differently in relation to the P—C—P bridge. In (I), the C2—C3 bond is trans with respect to the C1—P2 bond [P2—C1—C2—C3 176.44 (16)°], while it is gauche with respect to the C1—P1 bond [P1—C1—C2—C3 54.7 (2)°]. For the pyrrolidinyl bisphosphonate, the C2—C3 bond is gauche with respect to both bonds, the corresponding torsion angles being −43.6 (2) and 85.46 (19)°, respectively.
As shown by the value of the O7—C1—C2—C3 torsion angle [−70.3 (2)°], the orientation of the hydroxyl atom O7 with respect to the C—C—C—N chain is gauche. This indicates that the conformation around the O—C—C—C—N backbone in (I) is similar to that in disodium 3-ammonium-1-hydroxypropylidene-1,1-bisphosphonate pentahydrate (pamidronate), but it is different with respect to that of the pyrrolidinyl bisphosphonate, where the backbone is planar (Fernández & Vega, 2003). As noted earlier, this could be an effect of the intermolecular interactions in which the hydroxyl O atom is engaged. Although atom O7 forms comparable interactions as a donor in both (I) and the pyrrolidinyl bisphosphonate, it is a weaker acceptor in the latter [D···A 3.011 (2) Å, H···A 2.41 Å and D—H···A 129°] than in (I) (see Table 2). Given the limited amount of evidence available, it was stated in a previous work that the conformation of the backbone is defined by the pattern of atomic substitution of the N atom (Fernández & Vega, 2003). In the light of the results presented here, it becomes clear that this does not constitute the major contributor to the stability of the O—C—C—C—N backbone, but rather it comes from the hydrogen bonding.
The piperidinyl ring in (I) is puckered with respect to the most symmetric conformation of a six-membered ring (Duax et al., 1976). The ring-puckering parameters (Cremer & Pople, 1975) for the sequence N1/C4/C5/C6/C7/C8 are q2 0.011 (2) Å, q3 0.577 (2) Å and ϕ2 45 (12)°. The value of the phase indicates that the conformation of the ring is an almost perfect chair (Allen et al., 1991). Atoms N1 and C6 are located at 0.678 (3) and −0.672 (4) Å, respectively, from the least-squares plane defined by C4/C5/C7/C8 (r.m.s. deviation of fitted atoms 0.005 Å).
The hydrogen-bonding scheme for (I) consists of O—H···O and N—H···O types of interaction (Table 2). The hydrogen bonds between phosphonyl O atoms pack a pair of zwitterions into a head-to-head dimer (Fig. 2). The O atoms involved in these interactions, namely atoms O2, O3, O4 and O5, form an eight-membered P—O—H···O—P—O···H—O ring. The interactions between the phosphonyl atoms O1, O5 and O6, as well as the hydroxyl group, associate the dimers within a plane parallel to the crystallographic b and c axes. The N atom of the piperidinyl ring acts as a bifurcated donor of hydrogen bonds to the phosphonyl and hydroxyl O atoms of a neighbouring zwitterion.