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ISSN: 2056-9890

Methyl­phospho­nic acid, CH3PO(OH)2

aInstitute of Chemistry of New Materials, University of Osnabrück, Barbarastrasse 7, 49069 Osnabrück, Germany
*Correspondence e-mail: hreuter@uos.de

(Received 12 February 2014; accepted 17 February 2014; online 26 February 2014)

The asymmetric unit of the title compound, CH5O3P, contains two independent mol­ecules with nearly identical bond lengths and angles. In the crystal, each of the mol­ecules acts as acceptor (P=O) and donor (P—OH) of four hydrogen bonds to three adjacent mol­ecules, resulting in the formation of two different bilayers (one for each mol­ecule) stacked perpendicular to the a axis in the crystal.

Related literature

For organic and inorganic tin compounds of methyl phospho­nic acid, see: Adair et al. (1998[Adair, B., Natarajan, S. & Cheetham, A. K. (1998). J. Mater. Chem. 8, 1477-1479.]); Ribot et al. (2001[Ribot, F., Sanchez, C., Biesemans, M., Mercier, F. A. G., Martins, J. C., Gielen, M. & Willem, R. (2001). Organometallics, 20, 2593-2603.]). For structural data on phenyl phospho­nic acid, see: Weakley (1976[Weakley, T. J. R. (1976). Acta Cryst. B32, 2889-2890.]); Mahmoudkhani & Langer (2002[Mahmoudkhani, A. H. & Langer, V. (2002). J. Mol. Struct. 609, 97-108.]). For a brief communication on the unit-cell parameters of methyl phospho­nic acid, see: Kodolov et al. (1977[Kodolov, V. I., Povslugar, V. I., Alyamovskii, S. I. & Pletnev, R. N. (1977). Russ. Chem. Bull. pp. 142-143.]). For comparative studies of dimeric carb­oxy­lic acids, see: Allan et al. (2000)[Allan, D. R., Clark, S. J., Parsons, S. & Ruf, M. (2000). J. Phys. Condens. Matter, 12, L613-L618.]; Bruno & Randaccio (1980[Bruno, G. & Randaccio, L. (1980). Acta Cryst. B36, 1711-1712.]).

[Scheme 1]

Experimental

Crystal data
  • CH5O3P

  • Mr = 96.02

  • Monoclinic, P 21 /c

  • a = 15.1015 (8) Å

  • b = 5.7704 (3) Å

  • c = 9.9549 (6) Å

  • β = 108.262 (2)°

  • V = 823.79 (8) Å3

  • Z = 8

  • Mo Kα radiation

  • μ = 0.51 mm−1

  • T = 200 K

  • 0.45 × 0.26 × 0.12 mm

Data collection
  • Bruker APEXII CCD diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2009[Bruker (2009). APEX2, SADABS and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.805, Tmax = 0.942

  • 58588 measured reflections

  • 1989 independent reflections

  • 1763 reflections with I > 2σ(I)

  • Rint = 0.075

Refinement
  • R[F2 > 2σ(F2)] = 0.028

  • wR(F2) = 0.087

  • S = 1.08

  • 1989 reflections

  • 97 parameters

  • H-atom parameters constrained

  • Δρmax = 0.33 e Å−3

  • Δρmin = −0.35 e Å−3

Table 1
Selected bond lengths (Å)

P1—O13 1.4993 (11)
P1—O11 1.5441 (11)
P1—O12 1.5443 (12)
P1—C1 1.7586 (17)
P2—O23 1.4989 (11)
P2—O21 1.5478 (11)
P2—O22 1.5504 (12)
P2—C2 1.7612 (17)

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O22—H22⋯O23i 0.96 1.59 2.5528 (15) 180
O21—H21⋯O23ii 0.96 1.65 2.5768 (16) 161
O12—H12⋯O13iii 0.96 1.61 2.5649 (15) 174
O11—H11⋯O13iv 0.96 1.62 2.5671 (16) 169
Symmetry codes: (i) -x, -y+2, -z+1; (ii) [-x, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]; (iii) -x+1, -y+1, -z+1; (iv) [-x+1, y+{\script{1\over 2}}, -z+{\script{3\over 2}}].

Data collection: APEX2 (Bruker, 2009[Bruker (2009). APEX2, SADABS and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2009[Bruker (2009). APEX2, SADABS and SAINT. 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: DIAMOND (Brandenburg, 2006[Brandenburg, K. (2006). DIAMOND. Crystal Impact GbR, Bonn, Germany.]) and Mercury (Macrae et al., 2008[Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466-470.]); software used to prepare material for publication: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]).

Supporting information


Experimental top

Synthesis and crystallization top

Single crystals of methyl phospho­nic acid (Merck-Schuchardt) were obtained as side products from several experiments when we tried to growth singles crystals of diorganotin(IV) methyl phospho­nates by solvent evaporation. A suitable single crystal was selected under a polarization microscope and mounted on a 50 µm MicroMesh MiTeGen MicromountTM using FROMBLIN Y perfluoro­polyether (LVAC 16/6, Aldrich).

Refinement top

All hydrogen atoms could be localized in difference Fourier synthesis. Those of the methyl groups were idealized and refined at calculated positions riding on the carbon atoms with C—H distance of 0.98 Å. Those of the hydroxyl groups were refined with respect to a common O—H distance of 0.96 Å before they were fixed and allowed to ride on the corresponding oxygen atoms. For the hydrogen atoms of each methyl group a common isotropic displacement parameter was refined as well as one common isotropic displacement parameter for the hydrogen atoms of all hydroxyl groups.

Results and discussion top

Methyl­phospho­nic acid, CH3PO(OH)2, is a well-established reagent in inorganic as well as in organometallic chemistry forming numerous salts respectively coordination compounds with a lot of different metals and organometallic fragments. For an example, from tin(II) the synthesis and structural characterization of the mixed methyl­phospho­nate oxalate Sn2(MePO3)(C2O4) was described by Adair et al. (1998) whereas diorganotin(IV) moieties will give rise to the formation of dimeric species like [Bu2Sn(MePO(OH))2]2 as was shown by Ribot et al. (2001). During a systematic study on the complex formation of methyl­phospho­nic acid towards other organotin(IV) compounds we became aware, that the crystal structure of the title compound was never determined in detail. Only Kodolov et al. (1977) referred in a brief communication to the cell parameters of a monoclinic unit cell but no atomic coordinates were given.

During our studies, we never were able to confirm these cell parameters, although we also found a monoclinic unit cell. Moreover, we observed a strong broadening and multiplication of the reflections on cooling down the crystal to 100 K. For this reason, we present the results of a measurement at T = 200 K, before reflection broadening started.

The asymmetric unit of the title compound consists of two crystallographic independent molecules (Fig. 1) with nearly identical geometrical parameters (Tab. 1). These values correspond very well with those of phenyl phospho­nic acid that was determined by Mahmoudkhani et al. (2002) at T = 183 (2) K [d(P—O) = 1.536 (2) Å, 1.555 (2) Å; d(P=O) = 1.506 (2) Å and d(P—C) = 1.782 (3) Å] and Weakley (1976) at ambient temperature [d(P—O) = 1.539 (3) Å, 1.550 (4) Å; d(P=O) = 1.496 (4) Å and d(P—C) = 1.773 (5) Å]. With respect to bond angles at phospho­rous, tetra­hedral environment is much more distorted in the present compound [103.46 (8)° -112.94 (7)°] than in the corresponding phenyl compound [106.9 (2)° - 112.1 (2)°, Weakley (1976); 107.5 (1)°-111.7 (1)°, Mahmoudkhani et al. (2002)]

Each of the two molecules in the asymmetric unit is involved into four hydrogen bonds with molecules of the same kind giving rise to two different bilayers stacked perpendicular to the crystallographic a-axis (Fig. 2). Within each bilayer, each molecule of the upper layer is hydrogen bonded to three molecules of the lower layer and vice versa. In summary, the arrangement of the phospho­rous atoms in each bilayer corresponds to the arrangement of the arsenic atoms in the double-layer structure of grey arsenic consisting of an extended network of fused, six-membered rings of arsenic atoms with chair conformation.

Two of the four hydrogen bonds of each molecule result from centrosymmetric dimers (Fig. 3) in which one hydroxyl group (O22—H22) acts as donor and the double-bonded oxygen atom (O22) as acceptor for almost linear hydrogen bonds with a bond angle H···O—P of about 120° at the double bonded oxygen atom. These dimers are very similar those found in carbonic acids like propionic acid (Allan et al. 2000) or benzoic acid (Bruno & Randaccio, 1980). The double bonded oxygen atoms, additionally, are involved into a second pair of inter­molecular hydrogen bonds to the second hydroxyl group. These hydrogen bonds, also being less linear as the former one, are of similar length (Tab. 2).

Related literature top

For organic and inorganic tin compounds of methyl phosphonic acid, see: Adair et al. (1998); Ribot et al. (2001). For structural data on phenyl phosphonic acid, see: Weakley (1976); Mahmoudkhani & Langer (2002). For a brief communication on the unit-cell parameters of methyl phosphonic acid, see: Kodolov et al. (1977). For comparative studies of dimeric carboxylic acids, see: Allan et al. (2000); Bruno & Randaccio (1980).

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. Ball-and-stick model of the two molecules in the asymmetric unit of the title compound with the atomic numbering scheme used; with exception of the hydrogen atoms, which are shown as spheres with a common isotropic radius, all other atoms are represented as thermal displacement ellipsoids at the 50% probability level; hydrogen bonds are indicated by broken sticks (red).
[Figure 2] Fig. 2. Simplified ball-and-stick model of the crystal packing of MePO(OH)2 showing its bilayer structure; color code: oxygen = red, phosphorous = orange, carbon = dark grey, hydrogen = light grey; hydrogen bonds are shown as broken sticks (red).
[Figure 3] Fig. 3. Hydrogen bonding system in the bilayer of MePO(OH)2 resulting from molecule 2; with exception of the hydrogen atoms, which are shown as spheres with a common isotropic radius, all other atoms are represented as thermal displacement ellipsoids at the 50% probability level; methyl groups are omitted for clarity; hydrogen bonds are indicated by broken sticks (red); small black balls = center of symmetry; symmetry transformations used to generate equivalent atoms: 1) -x, 2 - y, 1 - z; 2) -x, 1/2 + y, 3/2 - z; 3) -x, -1/2 + y, 3/2 - z.
Methylphosphonic acid top
Crystal data top
CH5O3PF(000) = 400
Mr = 96.02Dx = 1.548 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 9876 reflections
a = 15.1015 (8) Åθ = 2.8–28.7°
b = 5.7704 (3) ŵ = 0.51 mm1
c = 9.9549 (6) ÅT = 200 K
β = 108.262 (2)°Rhomboidal plate, colourless
V = 823.79 (8) Å30.45 × 0.26 × 0.12 mm
Z = 8
Data collection top
Bruker APEXII CCD
diffractometer
1989 independent reflections
Radiation source: fine-focus sealed tube1763 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.075
φ and ω scansθmax = 28.0°, θmin = 2.8°
Absorption correction: multi-scan
(SADABS; Bruker, 2009)
h = 1919
Tmin = 0.805, Tmax = 0.942k = 77
58588 measured reflectionsl = 1313
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)] = 0.028H-atom parameters constrained
wR(F2) = 0.087 w = 1/[σ2(Fo2) + (0.0446P)2 + 0.3474P]
where P = (Fo2 + 2Fc2)/3
S = 1.08(Δ/σ)max = 0.001
1989 reflectionsΔρmax = 0.33 e Å3
97 parametersΔρmin = 0.35 e Å3
0 restraintsExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0089 (18)
Crystal data top
CH5O3PV = 823.79 (8) Å3
Mr = 96.02Z = 8
Monoclinic, P21/cMo Kα radiation
a = 15.1015 (8) ŵ = 0.51 mm1
b = 5.7704 (3) ÅT = 200 K
c = 9.9549 (6) Å0.45 × 0.26 × 0.12 mm
β = 108.262 (2)°
Data collection top
Bruker APEXII CCD
diffractometer
1989 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2009)
1763 reflections with I > 2σ(I)
Tmin = 0.805, Tmax = 0.942Rint = 0.075
58588 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0280 restraints
wR(F2) = 0.087H-atom parameters constrained
S = 1.08Δρmax = 0.33 e Å3
1989 reflectionsΔρmin = 0.35 e Å3
97 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
xyzUiso*/Ueq
P10.41034 (3)0.35924 (6)0.60908 (4)0.02670 (13)
O110.40297 (9)0.4245 (2)0.75562 (13)0.0446 (3)
H110.44330.54500.80660.070 (4)*
O120.38152 (8)0.5724 (2)0.51127 (14)0.0466 (3)
H120.42510.63630.46910.070 (4)*
O130.50590 (7)0.2779 (2)0.61564 (12)0.0365 (3)
C10.32469 (13)0.1438 (3)0.5486 (2)0.0480 (5)
H1110.32120.09820.45220.083 (5)*
H1120.26410.20450.54880.083 (5)*
H1130.34110.00860.61110.083 (5)*
P20.09029 (3)0.86636 (6)0.69483 (4)0.02720 (13)
O210.09504 (9)0.9190 (2)0.84939 (12)0.0459 (3)
H210.04951.02990.85680.070 (4)*
O220.11315 (8)1.0935 (2)0.62934 (12)0.0414 (3)
H220.07121.14400.54040.070 (4)*
O230.00227 (7)0.7710 (2)0.60798 (11)0.0377 (3)
C20.18264 (13)0.6703 (3)0.71256 (18)0.0436 (4)
H2110.17000.52600.75510.069 (4)*
H2120.24090.73850.77330.069 (4)*
H2130.18850.63730.61910.069 (4)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
P10.0301 (2)0.0254 (2)0.0277 (2)0.00282 (13)0.01342 (15)0.00150 (13)
O110.0563 (7)0.0486 (7)0.0382 (6)0.0219 (6)0.0283 (6)0.0172 (5)
O120.0384 (6)0.0457 (7)0.0635 (8)0.0146 (5)0.0269 (6)0.0244 (6)
O130.0345 (6)0.0381 (6)0.0405 (6)0.0082 (5)0.0172 (5)0.0157 (5)
C10.0487 (10)0.0457 (10)0.0550 (11)0.0194 (8)0.0239 (9)0.0222 (8)
P20.0305 (2)0.0268 (2)0.0223 (2)0.00449 (13)0.00533 (15)0.00254 (12)
O210.0605 (8)0.0509 (7)0.0246 (5)0.0224 (6)0.0108 (5)0.0001 (5)
O220.0369 (6)0.0361 (6)0.0413 (6)0.0076 (5)0.0019 (5)0.0111 (5)
O230.0345 (6)0.0411 (6)0.0329 (5)0.0065 (5)0.0038 (4)0.0135 (5)
C20.0449 (9)0.0420 (9)0.0392 (9)0.0169 (8)0.0065 (7)0.0033 (7)
Geometric parameters (Å, º) top
P1—O131.4993 (11)P2—O231.4989 (11)
P1—O111.5441 (11)P2—O211.5478 (11)
P1—O121.5443 (12)P2—O221.5504 (12)
P1—C11.7586 (17)P2—C21.7612 (17)
O11—H110.9583O21—H210.9584
O12—H120.9584O22—H220.9580
C1—H1110.9800C2—H2110.9800
C1—H1120.9800C2—H2120.9800
C1—H1130.9800C2—H2130.9800
O13—P1—O11112.86 (7)O23—P2—O21112.94 (7)
O13—P1—O12110.73 (6)O23—P2—O22110.99 (6)
O11—P1—O12108.17 (8)O21—P2—O22107.75 (7)
O13—P1—C1112.85 (8)O23—P2—C2112.83 (8)
O11—P1—C1103.46 (8)O21—P2—C2103.76 (7)
O12—P1—C1108.39 (9)O22—P2—C2108.15 (9)
P1—O11—H11117.1P2—O21—H21113.4
P1—O12—H12119.1P2—O22—H22118.4
P1—C1—H111109.5P2—C2—H211109.5
P1—C1—H112109.5P2—C2—H212109.5
H111—C1—H112109.5H211—C2—H212109.5
P1—C1—H113109.5P2—C2—H213109.5
H111—C1—H113109.5H211—C2—H213109.5
H112—C1—H113109.5H212—C2—H213109.5
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O22—H22···O23i0.961.592.5528 (15)180
O21—H21···O23ii0.961.652.5768 (16)161
O12—H12···O13iii0.961.612.5649 (15)174
O11—H11···O13iv0.961.622.5671 (16)169
Symmetry codes: (i) x, y+2, z+1; (ii) x, y+1/2, z+3/2; (iii) x+1, y+1, z+1; (iv) x+1, y+1/2, z+3/2.
Selected bond lengths (Å) top
P1—O131.4993 (11)P2—O231.4989 (11)
P1—O111.5441 (11)P2—O211.5478 (11)
P1—O121.5443 (12)P2—O221.5504 (12)
P1—C11.7586 (17)P2—C21.7612 (17)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O22—H22···O23i0.961.592.5528 (15)179.5
O21—H21···O23ii0.961.652.5768 (16)161.2
O12—H12···O13iii0.961.612.5649 (15)173.5
O11—H11···O13iv0.961.622.5671 (16)169.3
Symmetry codes: (i) x, y+2, z+1; (ii) x, y+1/2, z+3/2; (iii) x+1, y+1, z+1; (iv) x+1, y+1/2, z+3/2.
 

Acknowledgements

We thank the Deutsche Forschungsgemeinschaft and the Government of Lower Saxony for funding the diffractometer.

References

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