The title compound (H2DTMSP[EBP]), C14H36O6P2Si2, was crystallized by the slow evaporation of a solution in a 20:1 mixture of pentane and acetone. The H2DTMSP[EBP] molecule lies about an inversion center. In the solid state, the molecule exists in an anti configuration, with the molecular backbone C-C bond located on an inversion center. The compound exists in the solid state as hydrogen-bonded infinite sheets in the ab plane, unlike the methylene analogue, which exists as hydrogen-bonded infinite chains, demonstrating an `even-odd' effect of the length of the backbone alkyl chain.
Supporting information
CCDC reference: 638345
The title compound, which was prepared by a DCC-coupling procedure as previously
described, was initially isolated as a colourless viscous oil in 96% yield
(Griffith-Dzielawa et al., 2000). X-ray diffraction quality crystals
were obtained by very slow evaporation of a 20:1 (v/v)
pentane–acetone solution at 253 K. The purity of the compound was established
by potentiometric titration, 31P NMR spectroscopy and melting point. The
equivalent weight was determined by titrating a weighed amount of the compound
in a 2:1 (v/v) propan-2-ol–toluene solution with 0.1 M
NaOH using an Orion EA 940 pH meter. The 31P NMR spectrum was obtained on a
VXR 400 MHz s pectrometer using CDCl3 as the solvent. The melting point was
measured using an Arthur H. Thomas, Hoover, capillary melting-point apparatus
with a calibrated thermometer [m.p. 364 (1) K (literature value 363–365 K)].
Equivalent weight, calculated: 209 g mol-1; found: 212 g mol-1. 31P NMR
(CDCl3, versus external 85% H3PO4, δ, p.p.m.): 31.44 (s)
(literature value: 31.43).
H atoms were refined using a riding model with fixed individual displacement
parameters [Uiso(H) = 1.2Uiso(CCH2),
1.5Uiso(CMe) or 1.5Uiso(O)].
Data collection: CrysAlis CCD (Oxford, 2006); cell refinement: CrysAlis RED (Oxford, 2006); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXL97; software used to prepare material for publication: WinGX (Farrugia, 1999).
Bis[3-(trimethylsilyl)propyl] ethylenebisphosphonate
top
Crystal data top
C14H36O6P2Si2 | Dx = 1.219 Mg m−3 |
Mr = 418.55 | Melting point: 91(1) K |
Orthorhombic, Pbca | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ac 2ab | Cell parameters from 6010 reflections |
a = 7.6865 (3) Å | θ = 3.8–28.5° |
b = 11.0294 (8) Å | µ = 0.32 mm−1 |
c = 26.8912 (13) Å | T = 100 K |
V = 2279.8 (2) Å3 | Prism, colourless |
Z = 4 | 0.39 × 0.24 × 0.21 mm |
F(000) = 904 | |
Data collection top
Oxford Xcalibur3 CCD area-detector diffractometer | 2598 independent reflections |
Radiation source: Enhance (Mo) X-ray source | 2091 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.026 |
Detector resolution: 15.9890 pixels mm-1 | θmax = 27.5°, θmin = 4.0° |
ϕ and ω scans | h = −6→9 |
Absorption correction: numerical Analytical numerical absorption correction using a multifaceted crystal
model based on expressions derived by Clark & Reid (1995) | k = −12→14 |
Tmin = 0.923, Tmax = 0.948 | l = −32→34 |
10013 measured reflections | |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.033 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.087 | H-atom parameters constrained |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0448P)2 + 0.9918P] where P = (Fo2 + 2Fc2)/3 |
2598 reflections | (Δ/σ)max = 0.001 |
113 parameters | Δρmax = 0.40 e Å−3 |
0 restraints | Δρmin = −0.28 e Å−3 |
Crystal data top
C14H36O6P2Si2 | V = 2279.8 (2) Å3 |
Mr = 418.55 | Z = 4 |
Orthorhombic, Pbca | Mo Kα radiation |
a = 7.6865 (3) Å | µ = 0.32 mm−1 |
b = 11.0294 (8) Å | T = 100 K |
c = 26.8912 (13) Å | 0.39 × 0.24 × 0.21 mm |
Data collection top
Oxford Xcalibur3 CCD area-detector diffractometer | 2598 independent reflections |
Absorption correction: numerical Analytical numerical absorption correction using a multifaceted crystal
model based on expressions derived by Clark & Reid (1995) | 2091 reflections with I > 2σ(I) |
Tmin = 0.923, Tmax = 0.948 | Rint = 0.026 |
10013 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.033 | 0 restraints |
wR(F2) = 0.087 | H-atom parameters constrained |
S = 1.05 | Δρmax = 0.40 e Å−3 |
2598 reflections | Δρmin = −0.28 e Å−3 |
113 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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
C1 | 0.6663 (2) | 0.59694 (16) | 0.07682 (6) | 0.0228 (4) | |
H1A | 0.6451 | 0.5477 | 0.0476 | 0.027* | |
H1B | 0.5980 | 0.6706 | 0.0740 | 0.027* | |
C2 | 0.6139 (2) | 0.52865 (16) | 0.12270 (6) | 0.0230 (4) | |
H2A | 0.6298 | 0.5800 | 0.1516 | 0.028* | |
H2B | 0.6879 | 0.4580 | 0.1265 | 0.028* | |
C3 | 0.4235 (2) | 0.48836 (15) | 0.11960 (6) | 0.0207 (3) | |
H3A | 0.4096 | 0.4374 | 0.0905 | 0.025* | |
H3B | 0.3515 | 0.5597 | 0.1148 | 0.025* | |
C4 | 0.3418 (2) | 0.50535 (16) | 0.23040 (6) | 0.0275 (4) | |
H4A | 0.2966 | 0.4625 | 0.2587 | 0.041* | |
H4B | 0.2705 | 0.5750 | 0.2239 | 0.041* | |
H4C | 0.4587 | 0.5310 | 0.2372 | 0.041* | |
C5 | 0.4840 (3) | 0.27110 (16) | 0.18826 (7) | 0.0286 (4) | |
H5A | 0.6027 | 0.2977 | 0.1902 | 0.043* | |
H5B | 0.4725 | 0.2125 | 0.1621 | 0.043* | |
H5C | 0.4505 | 0.2349 | 0.2193 | 0.043* | |
C6 | 0.1140 (2) | 0.35234 (18) | 0.16084 (7) | 0.0301 (4) | |
H6A | 0.1149 | 0.3023 | 0.1316 | 0.045* | |
H6B | 0.0413 | 0.4218 | 0.1552 | 0.045* | |
H6C | 0.0693 | 0.3067 | 0.1884 | 0.045* | |
C7 | 0.9617 (2) | 0.55842 (14) | −0.01105 (5) | 0.0178 (3) | |
H7A | 0.8467 | 0.5412 | −0.0241 | 0.021* | |
H7B | 1.0341 | 0.5847 | −0.0386 | 0.021* | |
O1 | 0.85763 (14) | 0.78640 (10) | 0.01125 (4) | 0.0218 (3) | |
O2 | 1.12876 (14) | 0.70338 (11) | 0.05460 (4) | 0.0207 (3) | |
H2 | 1.1988 | 0.7091 | 0.0317 | 0.031* | |
O3 | 0.85071 (14) | 0.62689 (10) | 0.08024 (4) | 0.0197 (3) | |
Si1 | 0.34062 (6) | 0.40350 (4) | 0.175058 (16) | 0.01931 (13) | |
P1 | 0.94606 (5) | 0.67886 (4) | 0.033276 (15) | 0.01598 (12) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
C1 | 0.0122 (7) | 0.0296 (8) | 0.0267 (8) | −0.0002 (7) | 0.0004 (6) | 0.0032 (7) |
C2 | 0.0190 (8) | 0.0269 (8) | 0.0232 (8) | −0.0020 (7) | −0.0008 (7) | 0.0034 (7) |
C3 | 0.0166 (8) | 0.0223 (8) | 0.0232 (8) | −0.0006 (6) | −0.0007 (6) | 0.0022 (7) |
C4 | 0.0214 (9) | 0.0302 (9) | 0.0310 (9) | −0.0001 (7) | −0.0003 (7) | −0.0047 (7) |
C5 | 0.0339 (10) | 0.0248 (9) | 0.0270 (9) | 0.0032 (8) | −0.0014 (8) | 0.0033 (7) |
C6 | 0.0237 (9) | 0.0347 (10) | 0.0320 (9) | −0.0095 (8) | 0.0001 (8) | −0.0020 (8) |
C7 | 0.0163 (8) | 0.0207 (8) | 0.0166 (7) | −0.0003 (6) | −0.0015 (6) | −0.0008 (6) |
O1 | 0.0170 (6) | 0.0204 (5) | 0.0279 (6) | 0.0013 (5) | −0.0014 (5) | 0.0008 (5) |
O2 | 0.0136 (5) | 0.0267 (6) | 0.0217 (6) | −0.0016 (5) | −0.0013 (5) | −0.0022 (5) |
O3 | 0.0134 (5) | 0.0270 (6) | 0.0188 (5) | −0.0015 (5) | 0.0011 (4) | 0.0002 (5) |
Si1 | 0.0166 (2) | 0.0202 (2) | 0.0212 (2) | −0.00173 (18) | 0.00024 (18) | 0.00063 (18) |
P1 | 0.0123 (2) | 0.0181 (2) | 0.0175 (2) | −0.00018 (15) | −0.00055 (15) | −0.00101 (15) |
Geometric parameters (Å, º) top
C1—O3 | 1.4587 (18) | C5—H5A | 0.9600 |
C1—C2 | 1.500 (2) | C5—H5B | 0.9600 |
C1—H1A | 0.9700 | C5—H5C | 0.9600 |
C1—H1B | 0.9700 | C6—Si1 | 1.8708 (18) |
C2—C3 | 1.532 (2) | C6—H6A | 0.9600 |
C2—H2A | 0.9700 | C6—H6B | 0.9600 |
C2—H2B | 0.9700 | C6—H6C | 0.9600 |
C3—Si1 | 1.8722 (16) | C7—C7i | 1.537 (3) |
C3—H3A | 0.9700 | C7—P1 | 1.7888 (15) |
C3—H3B | 0.9700 | C7—H7A | 0.9700 |
C4—Si1 | 1.8645 (17) | C7—H7B | 0.9700 |
C4—H4A | 0.9600 | O1—P1 | 1.4898 (12) |
C4—H4B | 0.9600 | O2—P1 | 1.5407 (11) |
C4—H4C | 0.9600 | O2—H2 | 0.8200 |
C5—Si1 | 1.8635 (18) | O3—P1 | 1.5687 (11) |
| | | |
O3—C1—C2 | 108.80 (13) | H5A—C5—H5C | 109.5 |
O3—C1—H1A | 109.9 | H5B—C5—H5C | 109.5 |
C2—C1—H1A | 109.9 | Si1—C6—H6A | 109.5 |
O3—C1—H1B | 109.9 | Si1—C6—H6B | 109.5 |
C2—C1—H1B | 109.9 | H6A—C6—H6B | 109.5 |
H1A—C1—H1B | 108.3 | Si1—C6—H6C | 109.5 |
C1—C2—C3 | 110.92 (13) | H6A—C6—H6C | 109.5 |
C1—C2—H2A | 109.5 | H6B—C6—H6C | 109.5 |
C3—C2—H2A | 109.5 | C7i—C7—P1 | 113.00 (14) |
C1—C2—H2B | 109.5 | C7i—C7—H7A | 109.0 |
C3—C2—H2B | 109.5 | P1—C7—H7A | 109.0 |
H2A—C2—H2B | 108.0 | C7i—C7—H7B | 109.0 |
C2—C3—Si1 | 115.26 (11) | P1—C7—H7B | 109.0 |
C2—C3—H3A | 108.5 | H7A—C7—H7B | 107.8 |
Si1—C3—H3A | 108.5 | P1—O2—H2 | 109.5 |
C2—C3—H3B | 108.5 | C1—O3—P1 | 119.08 (10) |
Si1—C3—H3B | 108.5 | C5—Si1—C4 | 108.50 (8) |
H3A—C3—H3B | 107.5 | C5—Si1—C6 | 110.68 (9) |
Si1—C4—H4A | 109.5 | C4—Si1—C6 | 110.44 (8) |
Si1—C4—H4B | 109.5 | C5—Si1—C3 | 110.02 (8) |
H4A—C4—H4B | 109.5 | C4—Si1—C3 | 109.45 (8) |
Si1—C4—H4C | 109.5 | C6—Si1—C3 | 107.74 (8) |
H4A—C4—H4C | 109.5 | O1—P1—O2 | 115.09 (7) |
H4B—C4—H4C | 109.5 | O1—P1—O3 | 113.44 (7) |
Si1—C5—H5A | 109.5 | O2—P1—O3 | 100.98 (6) |
Si1—C5—H5B | 109.5 | O1—P1—C7 | 110.91 (7) |
H5A—C5—H5B | 109.5 | O2—P1—C7 | 108.49 (7) |
Si1—C5—H5C | 109.5 | O3—P1—C7 | 107.25 (7) |
| | | |
O3—C1—C2—C3 | −176.65 (13) | C1—O3—P1—O1 | 53.09 (13) |
C1—C2—C3—Si1 | −179.29 (12) | C1—O3—P1—O2 | 176.79 (11) |
C2—C1—O3—P1 | 169.72 (11) | C1—O3—P1—C7 | −69.73 (12) |
C2—C3—Si1—C5 | −54.44 (14) | C7i—C7—P1—O1 | −175.25 (14) |
C2—C3—Si1—C4 | 64.69 (14) | C7i—C7—P1—O2 | 57.42 (17) |
C2—C3—Si1—C6 | −175.19 (12) | C7i—C7—P1—O3 | −50.88 (17) |
Symmetry code: (i) −x+2, −y+1, −z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2···O1ii | 0.82 | 1.68 | 2.4986 (16) | 174 |
Symmetry code: (ii) x+1/2, −y+3/2, −z. |
Experimental details
Crystal data |
Chemical formula | C14H36O6P2Si2 |
Mr | 418.55 |
Crystal system, space group | Orthorhombic, Pbca |
Temperature (K) | 100 |
a, b, c (Å) | 7.6865 (3), 11.0294 (8), 26.8912 (13) |
V (Å3) | 2279.8 (2) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.32 |
Crystal size (mm) | 0.39 × 0.24 × 0.21 |
|
Data collection |
Diffractometer | Oxford Xcalibur3 CCD area-detector diffractometer |
Absorption correction | Numerical Analytical numerical absorption correction using a multifaceted crystal
model based on expressions derived by Clark & Reid (1995) |
Tmin, Tmax | 0.923, 0.948 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10013, 2598, 2091 |
Rint | 0.026 |
(sin θ/λ)max (Å−1) | 0.649 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.033, 0.087, 1.05 |
No. of reflections | 2598 |
No. of parameters | 113 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.40, −0.28 |
Selected geometric parameters (Å, º) topO1—P1 | 1.4898 (12) | O3—P1 | 1.5687 (11) |
O2—P1 | 1.5407 (11) | | |
| | | |
O1—P1—O2 | 115.09 (7) | O1—P1—C7 | 110.91 (7) |
O1—P1—O3 | 113.44 (7) | O2—P1—C7 | 108.49 (7) |
O2—P1—O3 | 100.98 (6) | O3—P1—C7 | 107.25 (7) |
| | | |
C1—O3—P1—C7 | −69.73 (12) | C7i—C7—P1—O3 | −50.88 (17) |
Symmetry code: (i) −x+2, −y+1, −z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2···O1ii | 0.82 | 1.68 | 2.4986 (16) | 174.0 |
Symmetry code: (ii) x+1/2, −y+3/2, −z. |
The title compound, H2DTMSP[EBP], (I), is the second member of a homologous series of symmetrically substituted alkylenebisphosphonic acids characterized by the P—(CH2)n—P molecular backbone (n = 1–6). This series of silyl-substituted partial esters was initially prepared and investigated as potential heavy metal ion extractants using supercritical carbon dioxide, SC—CO2, as the diluent (Griffith-Dzielawa et al., 2000; McAlister et al., 2001, 2002, 2004; Herlinger et al., 2003). The trimethylsilylpropyl group, TMSP, was shown to be effective in solubilizing bisphosphonic acids in SC—CO2, with the solubility of the TMSP partial esters showing a hydrocarbon-like even–odd effect that depends upon the number of –CH2– groups in the alkylene chain. Earlier studies revealed the remarkable effect that the separation between the P atoms in the alkylene chain has on the aggregation, complexation and solvent-extraction properties of symmetrically substituted alkylenebisphosphonic acids (Herlinger et al., 2003; Chiarizia & Herlinger, 2004).
The acid dissociation constants for the first three members (n = 1–3) of this series were determined in a 70:30 w/w methanol–water solvent by potentiometric titration and 31P NMR spectroscopy (Zalupski, Jensen et al., 2006; Zalupski, Chiarizia et al., 2006). The acid dissociation constants, K1 and K2, for these silyl-substituted bisphosphonic acids were found to follow a distance-dependent order of acid strength, due to the diminished inductive effect of the phosphonic acid groups upon each other as the chain length increases. The first member of the series, P,P'-di[3(trimethylsilyl)-1-propyl]methylenebisphosphonic acid, H2DTMSP[MBP], was found to be a stronger acid than H2DTMSP[EBP], but the difference in acidity was not as great as expected (Zalupski, Jensen et al., 2006; Zalupski, Chiarizia et al., 2006). Our current interest in this series of TMSP-containing bisphosphonic acids derives from the effect that the separation between the P atoms should have on their structural chemistry. The compounds could potentially find use in the assembly of extended supramolecular hydrogen-bonded networks, as activators in enzymatic reactions, or as models for enzyme inhibition and mechanism studies.
The title compound, (I), crystallizes with four molecules per unit cell and only one half molecule per asymmetric unit. In the solid state, the molecule exists in an anti configuration (Fig. 1), with the molecular backbone C—C bond located on an inversion centre. The molecule exhibits herringbone packing when viewed along the a axis. Each molecule of H2DTMSP[EBP] is hydrogen bonded to four other molecules through P═O···H—OP interactions to create infinite sheets in the ab plane. Each of these four hydrogen bonds is symmetry equivalent and the donor–acceptor distance is 2.4986 (16) Å. (Fig. 2)
In contrast, the crystal structure of the first member of this series, H2DTMSP[MBP], reveals a quite different pattern of hydrogen-bonding (McLauchlan et al., 2004). In the solid state, the molecules of H2DTMSP[MBP] are stitched together by hydrogen bonds to form an infinite chain along the a axis, with each molecule of H2DTMSP[MBP] bound by two hydrogen bonds to two neighbouring molecules, with average donor–acceptor distances of 2.506 (3) Å. The P═O, P—OH and P—OR distances and angles are comparable for H2DTMSP[EBP] and H2DTMSP[MBP].
In aromatic solvents such as toluene, the silyl-substituted alkylenebisphosphonic acids H2DTMSP[ABP] (n = 1–6) are strongly aggregated, exhibiting an even–odd effect as the number of –CH2– bridging groups varies. Results from vapour-phase osmometry suggest that the odd members of the series are strongly hydrogen-bonded dimers whereas the even members of the series are more highly aggregated, existing primarily as strongly hydrogen-bonded hexamers (Fig. 3). This effect is most likely due to the `zigzag' (herringbone-like) pattern adopted by the alkylene chain separating the P atoms. For the odd members of the series, the pattern directs both the P═O and POH groups of the phosphonic acid moieties to the same side of the alkylene chain, whereas for the even members of the series the phosphonic acid groups are on opposite sides of the chain. Thus, these two different orientations control the geometry of the hydrogen-bonded aggregates that can be formed (Chiarizia & Herlinger, 2004). In hydrogen-bonding solvents such as methanol, however, vapour-phase osmometry suggests that both the odd and even members of the series exist primarily as monomers. The even–odd effect appears to be reflected in the solid-state structures of the first two members of the series, though, with H2DTMSP[MBP] forming infinite chains and H2DTMSP[EBP] creating infinite sheets. Efforts to see if the same patterns emerge with the heavier members of the series are underway.