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The structures of monoclinic (C2/m) lithium di­hydrogenphosphate, LiH2PO2, and tetragonal (P41212) beryllium bis(di­hydrogenphosphate), Be(H2PO2)2, have been determined by single-crystal X-ray diffraction. The structures consist of layers of hypophosphite anions and metal cations in tetrahedral coordination by O atoms. Within the layers, the anions bridge four Li+ and two Be2+ cations, respectively. In LiH2PO2, the Li atom lies on a twofold axis and the H2PO2- anion has the PO2 atoms on a mirror plane. In Be(H2PO2)2, the Be atom lies on a twofold axis and the H2PO2- anion is in a general position.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270104013691/bc1045sup1.cif
Contains datablocks I, II, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270104013691/bc1045Isup2.hkl
Contains datablock I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270104013691/bc1045IIsup3.hkl
Contains datablock II

Comment top

Previous studies of anhydrous hypophosphites include KH2PO2, RbH2PO2 and CsH2PO2 (Naumova Kuratieva Podberezskaya & Naumov, 2004), NH4H2PO2 (Zachariasen & Mooney, 1934), Ca(H2PO2)2 (Goedkoop & Loopstra, 1959), CaNa(H2PO2)3 (Matsuzaki & Iitaka, 1969), Cu(H2PO2)2 (Naumov et al., 2002), Zn(H2PO2)2 (Weakley, 1979; Tanner et al., 1997), GeCl(H2PO2) and SnCl(H2PO2) (Weakley & Watt, 1979), La(H2PO2)3 (Tanner et al., 1999), Er(H2PO2)3 (Aslanov et al., 1975), and U(H2PO2)4 (Tanner et al., 1992). The limited number of compounds investigated is due to the difficulty of their preparation and crystal growth. This paper reports the results of our investigation of two further anhydrous hypophosphites, namely Li(H2PO2) and Be(H2PO2)2. The hygroscopic nature of alkali and alkaline-earth hypophosphites makes the growth of their crystals generally difficult. Nevertheless, crystals of these Li and Be hypophosphites were obtained and their structures determined by X-ray diffraction. An initial report (Naumova Kuratieva Naumov & Podberezskaya, 2004) on the synthesis, growth conditions and crystal chemistry analysis of Li(H2PO2) was presented at the National Conference on Crystal Growth (NCCG-2002, Moscow).

Both title structures are layered and contain metal cations in tetrahedral coordination by O. The coordination environments of the Li+ and Be2+ cations are similar in both structures but, due to the different cation/anion ratios, the environments of the hypophosphite anions are different. The H2PO2 anion has the shape of a slightly distorted tetrahedron, with the P atom at the centre and two O and two H atoms as vertices. It serves as a tetradentate and bidentate bridging ligand between the Li+ and Be2+ cations, respectively (Figs. 1 and 2). Separate layers are linked by van der Waals interactions (Figs. 3 and 4), with the shortest H···H distances between layers being 2.46 (5) and 2.70 (3) Å in Li(H2PO2) and Be(H2PO2)2, respectively.

Experimental top

For small quantities, metal hypophosphites are usually synthesized from the corresponding sulfates and nitrates (Romanova & Demidenko, 1975), or carbonates (Naumova Kuratieva Podberezskaya & Naumov, 2004), hydroxides and oxides (Brun et al., 1972), by reaction with hypophosphorous acid, or Na and Ba hypophosphites. All these precursors have been tried in this work. Crystals of lithium hypophosphite were finally grown from an aqueous solution of lithium oxalate and calcium hypophosphite. Crystal growth was achieved by means of periodic cooling and heating cycles between 293 and 283 K Not a wide range?, every 12 h for 4 d in a speciallly constructed apparatus (Naumova Kuratieva Naumov & Podberezskaya, 2004). The precursors used for the preparation of lithium hypophosphite may play a role in the crystal growth. The crystals had a plate-like habit with a maximum dimension of 0.7 mm. Crystals of beryllium hypophosphite were grown in a small quantity at room temperature from an aqueous solution of hypophosphorous acid and beryllium carbonate. The latter was prepared from Be(NO3)2 (aqueous) and Na2CO3 (aqueous). Carbon dioxide was removed under vacuum. The crystals had a prismatic habit with a maximum dimension of 0.5 mm.

Refinement top

In both structures, the H atoms were located from difference electron-density maps. Their positions were refined without any constraint. The refinement of the Be(H2PO2)2 structure was carried out on a twinned crystal, with refined volume fractions of 40 (4) and 60 (4)% for the two chiral twin components.

Computing details top

For both compounds, data collection: CD4CA0 (Enraf-Nonius, 1989); cell refinement: CD4CA0; data reduction: CADDAT (Enraf-Nonius, 1989); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The (001) layer in LiH2PO2. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
[Figure 2] Fig. 2. The (001) layer in Be(H2PO2)2. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
[Figure 3] Fig. 3. A packing diagram for the LiH2PO2 structure, viewed along [010].
[Figure 4] Fig. 4. A packing diagram for the Be(H2PO2)2 structure, viewed along [100].
(I) lithium dihydrogenphosphate(I) top
Crystal data top
LiH2PO2F(000) = 144
Mr = 71.93Dx = 1.547 Mg m3
Monoclinic, C2/mMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yCell parameters from 24 reflections
a = 9.3557 (11) Åθ = 10.2–16.6°
b = 5.3107 (7) ŵ = 0.62 mm1
c = 6.5432 (12) ÅT = 293 K
β = 108.259 (11)°Plate, colourless
V = 308.73 (8) Å30.47 × 0.43 × 0.09 mm
Z = 4
Data collection top
Enraf-Nonius CAD-4
diffractometer
306 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.041
Graphite monochromatorθmax = 25.7°, θmin = 3.3°
2θ/θ scansh = 1110
Absorption correction: empirical (using intensity measurements)
(CADDAT; Enraf-Nonius, 1989)
k = 16
Tmin = 0.741, Tmax = 0.946l = 07
430 measured reflections3 standard reflections every 60 min
329 independent reflections intensity decay: none
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.038All H-atom parameters refined
wR(F2) = 0.106 w = 1/[σ2(Fo2) + (0.0565P)2 + 0.3682P]
where P = (Fo2 + 2Fc2)/3
S = 1.15(Δ/σ)max < 0.001
329 reflectionsΔρmax = 0.38 e Å3
29 parametersΔρmin = 0.24 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: 0.16 (3)
Crystal data top
LiH2PO2V = 308.73 (8) Å3
Mr = 71.93Z = 4
Monoclinic, C2/mMo Kα radiation
a = 9.3557 (11) ŵ = 0.62 mm1
b = 5.3107 (7) ÅT = 293 K
c = 6.5432 (12) Å0.47 × 0.43 × 0.09 mm
β = 108.259 (11)°
Data collection top
Enraf-Nonius CAD-4
diffractometer
306 reflections with I > 2σ(I)
Absorption correction: empirical (using intensity measurements)
(CADDAT; Enraf-Nonius, 1989)
Rint = 0.041
Tmin = 0.741, Tmax = 0.9463 standard reflections every 60 min
430 measured reflections intensity decay: none
329 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0380 restraints
wR(F2) = 0.106All H-atom parameters refined
S = 1.15Δρmax = 0.38 e Å3
329 reflectionsΔρmin = 0.24 e Å3
29 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
Li0.00000.2503 (10)0.00000.0417 (12)
P0.30832 (9)0.50000.26808 (14)0.0539 (5)
H0.346 (4)0.317 (7)0.419 (5)0.077 (10)*
O10.4156 (3)0.50000.1435 (4)0.0451 (7)
O20.1438 (2)0.50000.1556 (4)0.0446 (7)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Li0.028 (2)0.036 (3)0.066 (3)0.0000.021 (2)0.000
P0.0225 (6)0.0985 (10)0.0443 (7)0.0000.0156 (4)0.000
O10.0332 (12)0.0454 (14)0.0678 (16)0.0000.0319 (11)0.000
O20.0210 (11)0.0464 (13)0.0672 (15)0.0000.0148 (10)0.000
Geometric parameters (Å, º) top
Li—O1i1.933 (4)P—O11.478 (2)
Li—O1ii1.933 (4)P—O21.484 (2)
Li—O21.936 (4)P—H1.35 (4)
Li—O2iii1.936 (4)O1—Lii1.933 (4)
Li—Liiii2.652 (11)O1—Liv1.933 (4)
Li—Liiv2.658 (11)O2—Liiii1.936 (4)
O1i—Li—O1ii93.1 (2)O1—P—H109.7 (14)
O1i—Li—O2113.84 (9)O2—P—H110.7 (15)
O1ii—Li—O2122.55 (10)P—O1—Lii135.99 (12)
O1i—Li—O2iii122.55 (10)P—O1—Liv135.99 (12)
O1ii—Li—O2iii113.84 (9)Lii—O1—Liv86.9 (2)
O2—Li—O2iii93.5 (2)P—O2—Li134.67 (12)
O1—P—O2120.30 (15)P—O2—Liiii134.67 (12)
Hvi—P—H92 (3)Li—O2—Liiii86.5 (2)
Symmetry codes: (i) x+1/2, y+1/2, z; (ii) x1/2, y1/2, z; (iii) x, y+1, z; (iv) x, y, z; (v) x+1/2, y+1/2, z; (vi) x, y+1, z.
(II) beryllium bis[dihydrogenphosphate(I)] top
Crystal data top
Be(H2PO2)2Dx = 1.833 Mg m3
Mr = 138.98Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P41212Cell parameters from 22 reflections
Hall symbol: P 4abw 2nwθ = 10.0–12.9°
a = 5.0117 (5) ŵ = 0.76 mm1
c = 20.051 (3) ÅT = 293 K
V = 503.62 (10) Å3Prism, colourless
Z = 40.4 × 0.3 × 0.3 mm
F(000) = 280
Data collection top
Enraf-Nonius CAD-4
diffractometer
599 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.032
Graphite monochromatorθmax = 29.9°, θmin = 4.1°
2θ/θ scansh = 66
Absorption correction: empirical (using intensity measurements)
(CADDAT; Enraf-Nonius, 1989)
k = 47
Tmin = 0.761, Tmax = 0.796l = 2728
1372 measured reflections3 standard reflections every 60 min
699 independent reflections intensity decay: none
Refinement top
Refinement on F2Hydrogen site location: difference Fourier map
Least-squares matrix: fullAll H-atom parameters refined
R[F2 > 2σ(F2)] = 0.033 w = 1/[σ2(Fo2) + (0.0592P)2]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.098(Δ/σ)max < 0.001
S = 1.08Δρmax = 0.28 e Å3
699 reflectionsΔρmin = 0.34 e Å3
43 parametersExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.018 (6)
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack (1983), with xx Friedel pairs
Secondary atom site location: difference Fourier mapAbsolute structure parameter: 0.0 (4)
Crystal data top
Be(H2PO2)2Z = 4
Mr = 138.98Mo Kα radiation
Tetragonal, P41212µ = 0.76 mm1
a = 5.0117 (5) ÅT = 293 K
c = 20.051 (3) Å0.4 × 0.3 × 0.3 mm
V = 503.62 (10) Å3
Data collection top
Enraf-Nonius CAD-4
diffractometer
599 reflections with I > 2σ(I)
Absorption correction: empirical (using intensity measurements)
(CADDAT; Enraf-Nonius, 1989)
Rint = 0.032
Tmin = 0.761, Tmax = 0.7963 standard reflections every 60 min
1372 measured reflections intensity decay: none
699 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.033All H-atom parameters refined
wR(F2) = 0.098Δρmax = 0.28 e Å3
S = 1.08Δρmin = 0.34 e Å3
699 reflectionsAbsolute structure: Flack (1983), with xx Friedel pairs
43 parametersAbsolute structure parameter: 0.0 (4)
0 restraints
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
Be0.0017 (6)0.0017 (6)0.00000.0326 (7)
P0.49154 (11)0.07089 (14)0.07203 (3)0.0378 (2)
O10.2219 (3)0.0397 (3)0.05763 (8)0.0426 (5)
O20.7104 (4)0.0440 (4)0.03120 (12)0.0725 (8)
H10.554 (4)0.028 (4)0.1381 (10)0.029 (6)*
H20.495 (3)0.315 (5)0.0620 (10)0.040 (7)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Be0.0268 (10)0.0268 (10)0.0443 (19)0.0030 (15)0.0033 (11)0.0033 (11)
P0.0221 (3)0.0480 (4)0.0432 (4)0.0023 (2)0.0026 (2)0.0100 (2)
O10.0241 (8)0.0595 (12)0.0442 (8)0.0057 (7)0.0036 (6)0.0137 (8)
O20.0236 (8)0.0925 (19)0.1014 (17)0.0017 (10)0.0111 (10)0.0487 (13)
Geometric parameters (Å, º) top
Be—O11.609 (3)P—O21.4848 (19)
Be—O1i1.609 (3)P—H11.38 (2)
Be—O2ii1.603 (3)P—H21.24 (3)
Be—O2iii1.603 (3)O2—Beiv1.603 (3)
P—O11.4888 (16)
O1—Be—O1i110.7 (3)H1—P—H2108.0 (14)
O2ii—Be—O1107.29 (9)O1—P—H2110.3 (8)
O2iii—Be—O1109.20 (10)O2—P—H2106.5 (8)
O2ii—Be—O1i109.20 (10)O2—P—H1107.6 (8)
O2iii—Be—O1i107.29 (9)O1—P—H1109.5 (8)
O2ii—Be—O2iii113.2 (3)P—O2—Beiv146.79 (18)
O1—P—O2114.78 (12)P—O1—Be135.86 (11)
Symmetry codes: (i) y, x, z; (ii) y, x1, z; (iii) x1, y, z; (iv) x+1, y, z.

Experimental details

(I)(II)
Crystal data
Chemical formulaLiH2PO2Be(H2PO2)2
Mr71.93138.98
Crystal system, space groupMonoclinic, C2/mTetragonal, P41212
Temperature (K)293293
a, b, c (Å)9.3557 (11), 5.3107 (7), 6.5432 (12)5.0117 (5), 5.0117 (5), 20.051 (3)
α, β, γ (°)90, 108.259 (11), 9090, 90, 90
V3)308.73 (8)503.62 (10)
Z44
Radiation typeMo KαMo Kα
µ (mm1)0.620.76
Crystal size (mm)0.47 × 0.43 × 0.090.4 × 0.3 × 0.3
Data collection
DiffractometerEnraf-Nonius CAD-4
diffractometer
Enraf-Nonius CAD-4
diffractometer
Absorption correctionEmpirical (using intensity measurements)
(CADDAT; Enraf-Nonius, 1989)
Empirical (using intensity measurements)
(CADDAT; Enraf-Nonius, 1989)
Tmin, Tmax0.741, 0.9460.761, 0.796
No. of measured, independent and
observed [I > 2σ(I)] reflections
430, 329, 306 1372, 699, 599
Rint0.0410.032
(sin θ/λ)max1)0.6090.702
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.038, 0.106, 1.15 0.033, 0.098, 1.08
No. of reflections329699
No. of parameters2943
H-atom treatmentAll H-atom parameters refinedAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.38, 0.240.28, 0.34
Absolute structure?Flack (1983), with xx Friedel pairs
Absolute structure parameter?0.0 (4)

Computer programs: CD4CA0 (Enraf-Nonius, 1989), CD4CA0, CADDAT (Enraf-Nonius, 1989), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEPIII (Burnett & Johnson, 1996), SHELXL97.

Selected geometric parameters (Å, º) for (I) top
Li—O1i1.933 (4)P—O21.484 (2)
Li—O21.936 (4)P—H1.35 (4)
P—O11.478 (2)
O1—P—O2120.30 (15)O1—P—H109.7 (14)
Hii—P—H92 (3)O2—P—H110.7 (15)
Symmetry codes: (i) x+1/2, y+1/2, z; (ii) x, y+1, z.
Selected geometric parameters (Å, º) for (II) top
Be—O11.609 (3)P—O21.4848 (19)
Be—O2i1.603 (3)P—H11.38 (2)
P—O11.4888 (16)P—H21.24 (3)
O1—P—O2114.78 (12)O1—P—H2110.3 (8)
H1—P—H2108.0 (14)O2—P—H2106.5 (8)
Symmetry code: (i) y, x1, z.
 

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