The bivalent metal hypophosphites Sr(H₂PO₂)₂, Pb(H₂PO₂)₂ and Ba(H₂PO₂)₂

The structures of isomorphous monoclinic strontium and lead bis­(di­hydrogenphosphate), Sr(H₂PO₂)₂ and Pb(H₂PO₂)₂, and orthorhombic barium bis­(di­hydrogen­phos­phate), Ba(H₂PO₂)₂, consist of layers of hypophosphite anions and metal cations exhibiting square antiprismatic coordination by O atoms. The Sr and Pb atoms are located on sites with point symmetry 2, and the Ba atoms are on sites with point symmetry 222. Within the layers, each anion bridges four metal cations.

S1. Comment

Although anhydrous metal hypophosphites find numerous practical applications and have been used for studies of various aspects of solid-state reactivity, their crystal structures are not adequately known and analyzed. A small number of studies of anhydrous hypophosphorous acid salts, namely NH₄H₂PO₂ (Zachariasen & Mooney, 1934), Ca(H₂PO₂)₂ (Goedkoop & Loopstra, 1959), CaNa(H₂PO₂)₃ (Matsuzaki & Iitaka, 1969), Zn(H₂PO₂)₂ (Weakley, 1979; Tanner et al., 1997), La(H₂PO₂)₃ (Tanner et al., 1999), Er(H₂PO₂)₃ (Aslanov et al., 1975) and U(H₂PO₂)₄ (Tanner et al., 1992), have been reported. The present paper continues our research on anhydrous hypophosphorous acid salts, which have included KH₂PO₂, RbH₂PO₂ and CsH₂PO₂ (Naumova et al., 2004), LiH₂PO₂ and Be(H₂PO₂)₂ (Naumov et al., 2004), and Cu(H₂PO₂)₂ (Naumov et al., 2002), and the coordination function of the hypophosphite anion. All known structures of bivalent metal hypophosphites have been shown to consist of layers. We report here the structures of the title compounds.

The structures of all three title compounds, Sr(H₂PO₂)₂, (I), Pb(H₂PO₂)₂, (II), and Ba(H₂PO₂)₂, (III), consist of layers formed by hypophosphite anions and metal cations. The Sr and Pb compounds are isostructural, and the Ba compound is very similar but the layers are oriented differently in the unit cell. All three structures exhibit square antiprismatic coordination of the metal cations by O atoms. Sr and Pb atoms are located on sites with point symmetry 2, and Ba atoms with point symmetry 222. These square antiprisms, which possess a psuedo-fourfold axis, share four edges within a layer (Fig. 1). Also within the layers, slightly distorted tetrahedral H₂PO₂²⁻ anions bridge four metal cations via O atoms (see Table 1 for angles). The H atoms are directed out of the layers (Fig. 2).

This contrasts with the situations in Be(H₂PO₂)₂ (Naumov et al., 2004), where the Be atom has tetrahedral coordination and the hypophosphite anion acts as a bidentate bridge, and in the structure of Ca(H₂PO₂)₂ (Goedkoop & Loopstra, 1959), where the anion acts as a tridentate bridge in combination with the distorted octahedral coordination sphere of the Ca atom. For the larger cations (Sr, Pb and Ba) more coordination sites are needed. This leads to changes in the linkage of metal cations by hypophosphite anions, even though the stoichiometry is the same. Thus in the isostructural Sr and Pb compounds, the cations have slightly distorted square antiprismatic coordination spheres and the hypophosphite anions play the role of a tetradentate bridge. The introduction of extra symmetry and the conservation of the tetradentate bridging role of hypophosphite anions leads to the structure of Ba(H₂PO₂)₂. The packing of layers in Sr(H₂PO₂)₂ and Pb(H₂PO₂)₂ (Fig. 3) differs very little from that in Ba(H₂PO₂)₂ (Fig. 4). The layers in both the Sr and the Pb hypophosphites are shifted along (001) by 0.533 Å in comparison with the Ba(H₂PO₂)₂ structure.

The structures are layered in (100) for Sr(H₂PO₂)₂ and Pb(H₂PO₂)₂ (Fig. 3), and (010) for Ba(H₂PO₂)₂ (Fig. 4). The unit-cell dimensions of title compounds are similar and can be transformed from Ba(H₂PO₂)₂ to Sr(H₂PO₂)₂ and (Pb(H₂PO₂)₂) by the matrix (0 1 0/ 1 0 0/ 0 0 − 1). Separate layers are linked by van der Waals interactions. The nearest H···H contacts between the layers are 2.50 (9) Å for Sr(H₂PO₂)₂, 2.32 (6) Å for Pb(H₂PO₂)₂ and 2.49 (7) Å for Ba(H₂PO₂)₂.

S2. Experimental

Crystals of the Sr, Pb and Ba hypophosphites were grown from aqueous solutions prepared by the reaction of hypophosphorous acid with the corresponding metal carbonates. Crystal growth was carried out at room temperature in a dry box. Powder diffraction analysis shows agreement between the bulk of products and single crystals. Powder patterns for Sr(H₂PO₂)₂, Pb(H₂PO₂)₂ and Ba(H₂PO₂)₂ are similar.

S3. Refinement

For (I), H atoms were located in a difference map and positional coordinates were refined freely. For (II), H atoms were placed in calculated positions and both angles (tetrahedral) and P—H distances were constrained (P—H = 1.40 Å). A similar approach was taken in (III), except that the P—H distances were refined. U_iso(H) values were fixed at 1.2U_eq of attached P atom. In (III), the highest and lowest peaks in the difference maps were 1.07 Å and 0.81 Å from the Ba atom, respectively.

Computing details

For all 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: BS (Kang & Ozawa, 2002); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. A representation of the BaO8 square antiprisms of Ba(H2PO2)2 stacking in layers perpendicular to [100].
	Fig. 2. The linkage of square antiprisms and the PO2H2 tetrahedra in the structure of Ba(H2PO2)2.
	Fig. 3. The packing of layers in the structure of Sr(H2PO2)2.
	Fig. 4. The packing of layers in the structure of Ba(H2PO2)2 [shown in the same orientation as two upper layers of the Sr(H2PO2)2 structure presented in Fig. 3].

(I) strontium bis(dihydrogenphosphate)

Crystal data

Sr(H2PO2)2	F(000) = 416
Mr = 217.59	Dx = 2.631 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 22 reflections
a = 15.6553 (16) Å	θ = 10.4–13.9°
b = 5.9436 (7) Å	µ = 10.31 mm^−1
c = 5.9177 (7) Å	T = 293 K
β = 93.905 (9)°	Prism, colourless
V = 549.36 (11) Å^3	0.08 × 0.08 × 0.08 mm
Z = 4

Data collection

Enraf–Nonius CAD-4 diffractometer	279 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.040
Graphite monochromator	θmax = 25.0°, θmin = 2.6°
2θ/θ scans	h = −18→18
Absorption correction: empirical (using intensity measurements) (CADDAT; Enraf–Nonius, 1989)	k = 0→7
Tmin = 0.426, Tmax = 0.438	l = 0→7
530 measured reflections	3 standard reflections every 60 min
477 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.030	Only H-atom coordinates refined
wR(F^2) = 0.072	w = 1/[σ^2(Fo^2) + (0.0363P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.79	(Δ/σ)max < 0.001
477 reflections	Δρmax = 0.96 e Å^−3
40 parameters	Δρmin = −0.68 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0067 (8)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Sr	0.0000	0.2507 (2)	0.2500	0.0163 (4)
P	0.13762 (9)	0.7515 (5)	0.2755 (2)	0.0171 (4)
H1	0.185 (4)	0.885 (13)	0.404 (10)	0.021*
H2	0.193 (4)	0.643 (13)	0.168 (10)	0.021*
O1	0.0868 (3)	0.9021 (8)	0.1124 (7)	0.0200 (11)
O2	0.0874 (3)	0.5969 (9)	0.4188 (7)	0.0194 (11)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sr	0.0251 (5)	0.0074 (5)	0.0163 (5)	0.000	0.0020 (3)	0.000
P	0.0196 (9)	0.0123 (8)	0.0194 (8)	0.0009 (15)	0.0016 (7)	−0.0006 (14)
O1	0.028 (3)	0.011 (3)	0.021 (2)	0.000 (2)	0.004 (2)	0.005 (2)
O2	0.026 (3)	0.014 (3)	0.019 (2)	0.000 (2)	0.004 (2)	0.004 (2)

Geometric parameters (Å, º)

Sr—O1^i	2.621 (5)	Sr—P^ii	3.6606 (15)
Sr—O1^ii	2.621 (5)	P—O1	1.504 (5)
Sr—O2^iii	2.627 (5)	P—O2	1.507 (5)
Sr—O2^iv	2.627 (5)	P—Sr^iii	3.6538 (15)
Sr—O2	2.630 (5)	P—Sr^i	3.6606 (15)
Sr—O2^v	2.630 (5)	P—Sr^viii	3.664 (3)
Sr—O1^vi	2.637 (5)	P—H1	1.30 (7)
Sr—O1^vii	2.637 (5)	P—H2	1.28 (7)
Sr—P^iii	3.6538 (15)	O1—Sr^i	2.621 (5)
Sr—P^iv	3.6538 (15)	O1—Sr^viii	2.637 (5)
Sr—P^i	3.6606 (15)	O2—Sr^iii	2.627 (5)
O1^i—Sr—O1^ii	139.4 (2)	O1^ii—Sr—P^i	159.37 (13)
O1^i—Sr—O2^iii	117.56 (13)	O2^iii—Sr—P^i	109.20 (10)
O1^ii—Sr—O2^iii	77.07 (13)	O2^iv—Sr—P^i	70.95 (10)
O1^i—Sr—O2^iv	77.07 (13)	O2—Sr—P^i	125.90 (12)
O1^ii—Sr—O2^iv	117.56 (13)	O2^v—Sr—P^i	54.51 (11)
O2^iii—Sr—O2^iv	139.7 (2)	O1^vi—Sr—P^i	91.17 (11)
O1^i—Sr—O2	143.99 (14)	O1^vii—Sr—P^i	88.50 (11)
O1^ii—Sr—O2	74.53 (15)	P^iii—Sr—P^i	108.01 (4)
O2^iii—Sr—O2	74.38 (16)	P^iv—Sr—P^i	71.99 (4)
O2^iv—Sr—O2	74.32 (11)	O1^i—Sr—P^ii	159.37 (13)
O1^i—Sr—O2^v	74.53 (15)	O1^ii—Sr—P^ii	20.22 (12)
O1^ii—Sr—O2^v	143.99 (14)	O2^iii—Sr—P^ii	70.95 (10)
O2^iii—Sr—O2^v	74.32 (11)	O2^iv—Sr—P^ii	109.20 (10)
O2^iv—Sr—O2^v	74.38 (16)	O2—Sr—P^ii	54.51 (11)
O2—Sr—O2^v	77.0 (2)	O2^v—Sr—P^ii	125.90 (12)
O1^i—Sr—O1^vi	73.98 (16)	O1^vi—Sr—P^ii	88.50 (11)
O1^ii—Sr—O1^vi	74.41 (11)	O1^vii—Sr—P^ii	91.17 (11)
O2^iii—Sr—O1^vi	143.79 (15)	P^iii—Sr—P^ii	71.99 (4)
O2^iv—Sr—O1^vi	74.63 (15)	P^iv—Sr—P^ii	108.01 (4)
O2—Sr—O1^vi	117.81 (13)	P^i—Sr—P^ii	179.58 (11)
O2^v—Sr—O1^vi	139.74 (13)	O1—P—O2	116.8 (2)
O1^i—Sr—O1^vii	74.41 (11)	Sr^iii—P—Sr^i	108.01 (4)
O1^ii—Sr—O1^vii	73.98 (16)	Sr^iii—P—Sr^viii	70.05 (4)
O2^iii—Sr—O1^vii	74.63 (15)	Sr^i—P—Sr^viii	69.97 (4)
O2^iv—Sr—O1^vii	143.79 (15)	Sr^iii—P—Sr	69.73 (5)
O2—Sr—O1^vii	139.74 (13)	Sr^i—P—Sr	69.66 (5)
O2^v—Sr—O1^vii	117.81 (13)	Sr^viii—P—Sr	108.25 (4)
O1^vi—Sr—O1^vii	76.4 (2)	O1—P—H1	106 (3)
O1^i—Sr—P^iii	109.12 (10)	O2—P—H1	110 (3)
O1^ii—Sr—P^iii	70.72 (10)	Sr^iii—P—H1	84 (3)
O2^iii—Sr—P^iii	20.51 (12)	Sr^i—P—H1	141 (3)
O2^iv—Sr—P^iii	159.91 (13)	Sr^viii—P—H1	81 (3)
O2—Sr—P^iii	91.70 (11)	Sr—P—H1	146 (3)
O2^v—Sr—P^iii	88.63 (10)	O1—P—H2	109 (3)
O1^vi—Sr—P^iii	125.28 (11)	O2—P—H2	112 (3)
O1^vii—Sr—P^iii	54.31 (11)	Sr^iii—P—H2	146 (3)
O1^i—Sr—P^iv	70.72 (10)	Sr^i—P—H2	88 (2)
O1^ii—Sr—P^iv	109.12 (10)	Sr^viii—P—H2	143 (3)
O2^iii—Sr—P^iv	159.91 (13)	Sr—P—H2	89 (3)
O2^iv—Sr—P^iv	20.51 (12)	H1—P—H2	102 (3)
O2—Sr—P^iv	88.63 (10)	P—O1—Sr^i	122.7 (3)
O2^v—Sr—P^iv	91.70 (11)	P—O1—Sr^viii	122.1 (2)
O1^vi—Sr—P^iv	54.31 (11)	Sr^i—O1—Sr^viii	106.02 (16)
O1^vii—Sr—P^iv	125.28 (11)	P—O2—Sr^iii	121.9 (3)
P^iii—Sr—P^iv	179.58 (11)	P—O2—Sr	122.8 (2)
O1^i—Sr—P^i	20.22 (12)	Sr^iii—O2—Sr	105.62 (16)

Symmetry codes: (i) −x, −y+1, −z; (ii) x, −y+1, z+1/2; (iii) −x, −y+1, −z+1; (iv) x, −y+1, z−1/2; (v) −x, y, −z+1/2; (vi) x, y−1, z; (vii) −x, y−1, −z+1/2; (viii) x, y+1, z.

(II) Lead bis(dihydrogenphosphate)

Crystal data

Pb(H2PO2)2	F(000) = 592
Mr = 337.16	Dx = 4.032 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 22 reflections
a = 15.516 (3) Å	θ = 10.4–13.8°
b = 6.0081 (12) Å	µ = 30.86 mm^−1
c = 5.9686 (12) Å	T = 293 K
β = 93.30 (3)°	Plate, colourless
V = 555.49 (19) Å^3	0.10 × 0.10 × 0.02 mm
Z = 4

Data collection

Enraf–Nonius CAD-4 diffractometer	284 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.024
Graphite monochromator	θmax = 25.0°, θmin = 2.6°
2θ/θ scans	h = −18→18
Absorption correction: integration SHELX76	k = 0→7
Tmin = 0.071, Tmax = 0.531	l = 0→7
528 measured reflections	3 standard reflections every 60 min
483 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.033	H-atom parameters constrained
wR(F^2) = 0.058	w = 1/[σ^2(Fo^2)] where P = (Fo^2 + 2Fc^2)/3
S = 0.99	(Δ/σ)max < 0.001
483 reflections	Δρmax = 0.94 e Å^−3
34 parameters	Δρmin = −0.90 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.00011 (8)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Pb	0.0000	0.2501 (4)	0.2500	0.0328 (3)
P	0.1391 (2)	0.753 (2)	0.2707 (7)	0.0413 (12)
H1	0.1927	0.8864	0.4118	0.050*
H2	0.1927	0.6251	0.1412	0.050*
O1	0.0882 (7)	0.902 (2)	0.1175 (17)	0.049 (3)
O2	0.0902 (6)	0.5945 (18)	0.4188 (16)	0.034 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb	0.0323 (5)	0.0333 (5)	0.0329 (5)	0.000	0.0018 (3)	0.000
P	0.033 (2)	0.047 (3)	0.044 (2)	−0.002 (7)	0.002 (2)	−0.030 (5)
O1	0.058 (8)	0.051 (9)	0.038 (7)	−0.007 (7)	0.000 (6)	0.011 (7)
O2	0.023 (6)	0.046 (8)	0.033 (6)	−0.001 (6)	0.003 (5)	−0.011 (6)

Geometric parameters (Å, º)

Pb—O1^i	2.679 (10)	P—O1	1.474 (13)
Pb—O1^ii	2.679 (10)	P—O2	1.531 (12)
Pb—O2^iii	2.656 (9)	P—H1	1.4000
Pb—O2^iv	2.656 (9)	P—H2	1.4000
Pb—O2	2.663 (10)	O1—Pb^viii	2.645 (12)
Pb—O2^v	2.663 (10)	O1—Pb^i	2.679 (10)
Pb—O1^vi	2.645 (12)	O2—Pb^iii	2.656 (9)
Pb—O1^vii	2.645 (12)
O1^vi—Pb—O1^vii	75.5 (5)	O2^v—Pb—O1^i	73.9 (4)
O1^vi—Pb—O2^iii	75.6 (4)	O1^vi—Pb—O1^ii	74.6 (4)
O1^vii—Pb—O2^iii	143.5 (3)	O1^vii—Pb—O1^ii	74.1 (2)
O1^vi—Pb—O2^iv	143.5 (3)	O2^iii—Pb—O1^ii	77.1 (3)
O1^vii—Pb—O2^iv	75.6 (4)	O2^iv—Pb—O1^ii	117.6 (3)
O2^iii—Pb—O2^iv	138.9 (5)	O2—Pb—O1^ii	73.9 (4)
O1^vi—Pb—O2	140.4 (3)	O2^v—Pb—O1^ii	143.9 (3)
O1^vii—Pb—O2	117.2 (3)	O1^i—Pb—O1^ii	140.1 (5)
O2^iii—Pb—O2	74.5 (3)	O1—P—O2	118.1 (5)
O2^iv—Pb—O2	73.8 (2)	O1—P—H1	107.8
O1^vi—Pb—O2^v	117.2 (3)	O2—P—H1	107.8
O1^vii—Pb—O2^v	140.4 (3)	O1—P—H2	107.8
O2^iii—Pb—O2^v	73.8 (2)	O2—P—H2	107.8
O2^iv—Pb—O2^v	74.5 (3)	H1—P—H2	107.1
O2—Pb—O2^v	78.0 (4)	P—O1—Pb^viii	124.2 (6)
O1^vi—Pb—O1^i	74.1 (2)	P—O1—Pb^i	122.1 (7)
O1^vii—Pb—O1^i	74.6 (4)	Pb^viii—O1—Pb^i	105.4 (4)
O2^iii—Pb—O1^i	117.6 (3)	P—O2—Pb^iii	120.7 (6)
O2^iv—Pb—O1^i	77.1 (3)	P—O2—Pb	122.2 (5)
O2—Pb—O1^i	143.9 (3)	Pb^iii—O2—Pb	105.5 (3)

Symmetry codes: (i) −x, −y+1, −z; (ii) x, −y+1, z+1/2; (iii) −x, −y+1, −z+1; (iv) x, −y+1, z−1/2; (v) −x, y, −z+1/2; (vi) −x, y−1, −z+1/2; (vii) x, y−1, z; (viii) x, y+1, z.

(III) Barium bis(dihydrogenphosphate) ?

Crystal data

Ba(H2PO2)2	F(000) = 488
Mr = 267.30	Dx = 2.958 Mg m^−3
Orthorhombic, Ccca	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: -C 2b 2bc	Cell parameters from 22 reflections
a = 6.2390 (8) Å	θ = 10–15°
b = 15.584 (3) Å	µ = 7.07 mm^−1
c = 6.1726 (13) Å	T = 296 K
V = 600.15 (19) Å^3	Plate, colourless
Z = 4	0.27 × 0.24 × 0.04 mm

Data collection

Enraf–Nonius CAD-4 diffractometer	269 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.085
Graphite monochromator	θmax = 29.2°, θmin = 2.6°
2θ/θ scans	h = 0→8
Absorption correction: empirical (using intensity measurements) (CADDAT; Enraf–Nonius, 1989)	k = −18→21
Tmin = 0.168, Tmax = 0.750	l = 0→8
671 measured reflections	3 standard reflections every 60 min
415 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.032	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.083	w = 1/[σ^2(Fo^2) + (0.0384P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.89	(Δ/σ)max < 0.001
415 reflections	Δρmax = 1.68 e Å^−3
20 parameters	Δρmin = −1.34 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0016 (5)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Ba	0.5000	0.2500	0.2500	0.0235 (3)
P	0.0000	0.10705 (15)	0.2500	0.0255 (4)
H1	0.115 (6)	0.059 (2)	0.368 (6)	0.031*
O1	0.1467 (6)	0.1571 (3)	0.1046 (7)	0.0316 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ba	0.0109 (3)	0.0433 (5)	0.0163 (3)	0.000	0.000	0.000
P	0.0172 (8)	0.0349 (11)	0.0243 (9)	0.000	−0.0006 (15)	0.000
O1	0.0200 (17)	0.048 (2)	0.027 (2)	−0.003 (2)	0.0012 (18)	0.005 (3)

Geometric parameters (Å, º)

Ba—O1^i	2.779 (4)	Ba—O1^vi	2.785 (4)
Ba—O1^ii	2.779 (4)	Ba—O1^vii	2.785 (4)
Ba—O1^iii	2.779 (4)	P—O1	1.501 (4)
Ba—O1^iv	2.779 (4)	P—O1^viii	1.501 (4)
Ba—O1	2.785 (4)	P—H1	1.27 (4)
Ba—O1^v	2.785 (4)	O1—Ba^iv	2.779 (4)
O1^i—Ba—O1^ii	141.53 (16)	O1^iv—Ba—O1^vi	74.70 (10)
O1^i—Ba—O1^iii	76.09 (18)	O1—Ba—O1^vi	142.40 (18)
O1^ii—Ba—O1^iii	117.22 (19)	O1^v—Ba—O1^vi	75.40 (18)
O1^i—Ba—O1^iv	117.22 (19)	O1^i—Ba—O1^vii	74.70 (10)
O1^ii—Ba—O1^iv	76.09 (18)	O1^ii—Ba—O1^vii	141.74 (17)
O1^iii—Ba—O1^iv	141.53 (16)	O1^iii—Ba—O1^vii	75.89 (15)
O1^i—Ba—O1	141.74 (17)	O1^iv—Ba—O1^vii	73.89 (9)
O1^ii—Ba—O1	74.70 (10)	O1—Ba—O1^vii	75.40 (18)
O1^iii—Ba—O1	73.89 (9)	O1^v—Ba—O1^vii	142.40 (18)
O1^iv—Ba—O1	75.89 (15)	O1^vi—Ba—O1^vii	117.38 (18)
O1^i—Ba—O1^v	75.89 (15)	O1—P—O1^viii	117.4 (4)
O1^ii—Ba—O1^v	73.89 (9)	O1—P—H1	108.0
O1^iii—Ba—O1^v	74.70 (10)	O1^viii—P—H1	108.0
O1^iv—Ba—O1^v	141.74 (17)	H1^viii—P—H1	107.2
O1—Ba—O1^v	117.38 (18)	P—O1—Ba^iv	122.7 (2)
O1^i—Ba—O1^vi	73.89 (9)	P—O1—Ba	124.1 (2)
O1^ii—Ba—O1^vi	75.89 (15)	Ba^iv—O1—Ba	104.11 (15)
O1^iii—Ba—O1^vi	141.74 (17)

Symmetry codes: (i) x+1/2, −y+1/2, z+1/2; (ii) x+1/2, y, −z; (iii) −x+1/2, y, z+1/2; (iv) −x+1/2, −y+1/2, −z; (v) −x+1, y, −z+1/2; (vi) −x+1, −y+1/2, z; (vii) x, −y+1/2, −z+1/2; (viii) −x, y, −z+1/2.