The first three-dimensional vanadium hypophosphite

The title synthesized hypophosphite has the formula V(H₂PO₂)₃. Its structure is based on VO₆ octa­hedra and (H₂PO₂)^- pseudo-tetra­hedra. The asymmetric unit contains two crystallographically distinct V atoms and six independent (H₂PO₂)^- groups. The connection of the polyhedra generates [VPO₆H₂]^6- chains extended along a, b and c, leading to the first three-dimensional network of an anhydrous transition metal hypophosphite.

S1. Comment

During the past few decades, several metal hypophosphite compounds have been reported in the literature, incorporating alkali, alkaline earth (Galigné & Dumas, 1973; Kuratieva et al., 2005), transition (Marcos et al., 1993, 1994; Kuratieva et al., 2002), lanthanide and group 14 metals. Several line of interest have led us to investigate this class of compounds. Among them are (i) the study of low-dimensional structures suitable for catalytic or ion-exchange properties supported by the low degree of connectivity of the oxoanion H₂PO₂^- ; (ii) the characterization of lanthanide ions involving the use of the (H₂PO₂)^- ligand (Seddon et al., 1999; Tanner et al., 1999, 2000); and (iii) the application of anhydrous metal hypophosphites as mild reducing agents, reagents in catalytic syntheses of organophosphorous compounds and antioxidants (Naumova et al., 2004a,b ?????). Another interest was the magnetic properties of some hypophosphite complexes of transtion metals (Marcos et al., 1992; Yoshida et al., 2009).

Although a number of crystal structures of hypophosphites are known, there is a lack of structural data for anhydrous transition metal hypophosphites. In fact, only two such compounds have been characterized by X-ray diffraction, namely Fe(H₂PO₂)₃ (Kuratieva & Naumov, 2006), exhibiting a layered structure built up from iron hypophosphite chains, and Zn(H₂PO₂)₂ (Tanner et al., 1997), comprising a two-dimensional structure.

At the same time and to the best of our knowledge, only one vanadium hypophosphite has been isolated. It is hydrated and exhibits a one-dimensional structure (Le Bail et al., 1994) where the metallic cation is involved in an oxovanadium group. The aim of our study is to enlarge the hypophosphite family compounds, especially for metals like vanadium, which adopts different coordination geometries.

Our study reports the first anhydrous vanadium phosphinate. The asymmetric unit (Fig. 1) contains two independent V atoms and six phosphinate ions, all situated on general positions. Atoms V1 and V2 both exhibit a slightly distorted octahedral geometry, where the mean values of the V—O bonds are 1.998 (3) Å and 1.997 (3) Å, respectively. The hypophosphite groups have pseudotetrahedral geometry. The bond distances and angles (Table 1) in the H₂PO₂^- pseudotetrahedra are similar to those observed in other hypophosphite compounds. The V^IIIO₆ octahedra share all their vertices with six distinct pseudotetrahedra, and each H₂PO₂^- anion has both of its O atoms linked to two adjacent metallic centers, acting as a bidentate bridging ligand. This type of connection involves the formation of V—O—P—O—V chains through the three directions of the space, leading therefore to a three-dimensional network. The junction of the V1, V2, O and P atoms along the a axis describes helicoidal chains, while along the c-axis direction it forms a sawtooth curve (Figs. 3a and 3b). Along the b axis, the V2—O—P—O—V2 chains follow a helicoidal pattern with an elliptical cross section and the V1—O—P—O—V1 chains might be assimilated to a sinusoid (Fig. 3c). While in the oxovanadium(IV) hypophosphite (Le Bail et al., 1994) the one-dimensional aspect of the structure is related to the anisotropic environment of the vanadium, in the title compound the three-dimensionality is favoured by the isotropic bonding scheme of the cation owing to its +3 oxidation state.

Related literature

For related literature, see: Galigné & Dumas (1973); Kuratieva, Naumova & Naumov (2005); Kuratieva et al. (2005); Marcos et al. (1992, 1993); Seddon et al. (1999); Tanner et al. (1997, 1999); Yoshida et al. (2009).

S2. Experimental

Vanadium(III) hypophosphite was synthesized by a hydrothermal method. A mixture of deionzed water, vanadium(V) oxide, 50% hypophosphoric acid and lithium carbonate in a molar ratio of 10.437:0.1:2:0.428 was placed in a Teflon acid digestion bomb (23 ml, Parr Instruments), heated at 423 K for 48 h and cooled to room temperature over a period of 24 h. The green product was filtered off, washed with deionized water and dried at room temperature in a desiccator.

The comparison of the X-ray powder diffraction pattern of the synthesized product with the simulated one from this structure revealed that the title compound is present as a minor phase. The major phase remains unknown.

While lithium ions are not present in this structure, the presence of lithium carbonate seems to be necessary to obtain the title compound, as synthesis attempts performed without the lithium source were unsuccessful.

We assume that the hypophosphoric acid is responsible of the reduction of the vanadium ions observed during the synthesis (V⁵⁺ to V³⁺), as no other reducing agent is present.

S3. Refinement

The H atoms were located in a Fourier difference map and their positional parameters were refined freely, while their U_iso(H) values were fixed at 0.049 Ų. The refinement of the structure was carried out on a twinned crystal. The transformation matrix used is (001, 010, 100). The refined volume fractions are 94.7 and 5.3%. [Please check modifications to text, inline with data in CIF.]

Computing details

Data collection: COLLECT (Nonius, 1998); cell refinement: DIRAX/LSQ (Duisenberg, 1992); data reduction: EVALCCD (Duisenberg, 1998); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2005); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. : The asymmetric unit of [V2P6O12H12]^12-; displacement ellipsoids of the independent atoms are plotted at the 50% probability level and H atoms are drawn as small spheres of arbitrary radii. [Symmetry codes: (i) x, y, z - 1; (ii) -x + 1/2, y + 1/2, -z + 1/2; (iii) -x + 1/2, y - 1/2, -z + 3/2; (iv) x + 1/2, -y + 1/2, z + 1/2; (v) x - 1/2, -y + 1/2, z + 1/2.]
	Fig. 2. : A perspective view of V(H2PO2)3 along the [001] direction.
	Fig. 3. : A representation of the V—O—P—O—V chains along (a) the [100] direction, (b) the [001] direction and (c) the [010] direction.

vanadium hypophosphite

Crystal data

V(H2PO2)3	F(000) = 976
Mr = 491.8	Dx = 2.11 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 9018 reflections
a = 11.4985 (3) Å	θ = 2.9–27.5°
b = 11.7771 (5) Å	µ = 1.88 mm^−1
c = 11.5999 (4) Å	T = 293 K
β = 99.807 (2)°	Prism, green
V = 1547.89 (9) Å^3	0.15 × 0.05 × 0.04 mm
Z = 4

Data collection

Nonius KappaCCD diffractometer	Rint = 0.117
CCD rotation images, thick slices scans	θmax = 27.5°, θmin = 3.6°
20258 measured reflections	h = −14→14
3550 independent reflections	k = −15→13
2426 reflections with I > 2σ(I)	l = −15→15

Refinement

Refinement on F^2	Only H-atom coordinates refined
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + (0.0199P)^2 + 4.0183P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.053	(Δ/σ)max = 0.006
wR(F^2) = 0.091	Δρmax = 0.50 e Å^−3
S = 1.04	Δρmin = −0.54 e Å^−3
3550 reflections	Extinction correction: (SHELXL97; Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
219 parameters	Extinction coefficient: 0.0013 (3)
0 restraints

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
V1	0.24603 (7)	0.18513 (6)	0.69692 (7)	0.01900 (19)
V2	0.22812 (6)	0.20319 (7)	0.18963 (7)	0.0203 (2)
P1	0.35198 (11)	−0.02754 (11)	0.30844 (13)	0.0302 (3)
P2	−0.04238 (10)	0.22262 (11)	0.06807 (11)	0.0245 (3)
P3	0.47390 (11)	0.34106 (12)	0.23653 (12)	0.0281 (3)
P4	0.30125 (14)	0.08384 (12)	0.95864 (12)	0.0357 (4)
P5	0.23503 (15)	0.41320 (12)	0.84204 (14)	0.0399 (4)
P6	0.11404 (12)	0.20824 (14)	0.42549 (12)	0.0334 (3)
O1	0.2886 (3)	0.5289 (3)	0.8650 (3)	0.0331 (8)
O2	0.3095 (3)	−0.1342 (3)	0.3592 (3)	0.0320 (8)
O3	−0.1071 (3)	0.3117 (3)	0.1251 (3)	0.0303 (8)
O4	0.2596 (3)	0.1751 (3)	1.0298 (3)	0.0377 (9)
O5	0.3366 (3)	0.1189 (3)	0.8447 (3)	0.0302 (8)
O6	0.6033 (3)	0.3188 (3)	0.2748 (3)	0.0300 (8)
O7	0.2806 (3)	0.3429 (3)	0.7523 (3)	0.0342 (9)
O8	0.2606 (3)	0.0390 (3)	0.2302 (4)	0.0415 (10)
O9	0.1450 (3)	0.2435 (3)	0.5517 (3)	0.0301 (8)
O10	0.0580 (3)	0.1621 (3)	0.1444 (3)	0.0332 (9)
O11	0.2025 (3)	0.2393 (4)	0.3511 (3)	0.0473 (11)
O12	0.3974 (3)	0.2392 (3)	0.2420 (3)	0.0409 (10)
H1A	0.401 (5)	0.035 (5)	0.403 (5)	0.049*
H1B	0.448 (5)	−0.043 (5)	0.247 (5)	0.049*
H2A	−0.118 (5)	0.142 (5)	0.003 (5)	0.049*
H2B	−0.001 (5)	0.278 (5)	−0.027 (5)	0.049*
H3A	0.451 (4)	0.423 (5)	0.311 (5)	0.049*
H3B	0.462 (5)	0.387 (5)	0.127 (5)	0.049*
H4A	0.205 (5)	0.013 (5)	0.935 (5)	0.049*
H4B	0.387 (4)	0.013 (5)	1.006 (5)	0.049*
H5A	0.224 (5)	0.365 (5)	0.936 (5)	0.049*
H5B	0.116 (5)	0.411 (5)	0.829 (5)	0.049*
H6A	0.091 (5)	0.095 (5)	0.421 (5)	0.049*
H6B	0.007 (5)	0.249 (5)	0.386 (5)	0.049*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
V1	0.0206 (4)	0.0182 (4)	0.0190 (4)	−0.0005 (3)	0.0058 (3)	−0.0008 (3)
V2	0.0204 (4)	0.0220 (4)	0.0187 (4)	−0.0005 (3)	0.0033 (3)	0.0005 (4)
P1	0.0271 (7)	0.0223 (7)	0.0383 (8)	−0.0031 (6)	−0.0028 (6)	0.0086 (6)
P2	0.0207 (6)	0.0283 (7)	0.0242 (7)	0.0002 (5)	0.0027 (5)	−0.0041 (6)
P3	0.0204 (6)	0.0313 (7)	0.0329 (8)	0.0017 (6)	0.0050 (5)	0.0047 (6)
P4	0.0600 (10)	0.0244 (7)	0.0273 (8)	0.0120 (7)	0.0201 (7)	0.0067 (6)
P5	0.0637 (10)	0.0181 (7)	0.0469 (10)	−0.0038 (7)	0.0351 (8)	−0.0032 (7)
P6	0.0290 (7)	0.0503 (9)	0.0208 (7)	−0.0022 (7)	0.0035 (5)	−0.0003 (7)
O1	0.046 (2)	0.0171 (17)	0.034 (2)	0.0030 (16)	0.0025 (17)	−0.0014 (16)
O2	0.045 (2)	0.0203 (18)	0.031 (2)	−0.0015 (16)	0.0077 (16)	0.0057 (15)
O3	0.0289 (17)	0.0278 (19)	0.038 (2)	0.0020 (16)	0.0153 (15)	−0.0021 (16)
O4	0.061 (2)	0.032 (2)	0.023 (2)	0.0132 (19)	0.0158 (18)	0.0015 (16)
O5	0.0291 (18)	0.043 (2)	0.0199 (18)	0.0078 (16)	0.0071 (15)	0.0030 (16)
O6	0.0160 (15)	0.049 (2)	0.0257 (18)	0.0016 (16)	0.0048 (13)	0.0000 (17)
O7	0.043 (2)	0.027 (2)	0.036 (2)	−0.0029 (17)	0.0155 (17)	−0.0055 (16)
O8	0.0305 (19)	0.029 (2)	0.059 (3)	0.0004 (17)	−0.0079 (18)	0.0171 (19)
O9	0.0386 (19)	0.0309 (19)	0.0213 (18)	0.0118 (16)	0.0067 (15)	0.0007 (15)
O10	0.0246 (17)	0.0252 (19)	0.047 (2)	0.0027 (15)	−0.0034 (16)	0.0076 (17)
O11	0.051 (2)	0.068 (3)	0.026 (2)	−0.016 (2)	0.0163 (18)	−0.007 (2)
O12	0.0247 (18)	0.044 (2)	0.050 (2)	−0.0100 (17)	−0.0043 (17)	0.0121 (19)

Geometric parameters (Å, º)

V1—O7	1.984 (3)	P3—O6	1.502 (3)
V1—O1^i	1.991 (3)	P3—H3A	1.35 (6)
V1—O9	1.998 (3)	P3—H3B	1.37 (6)
V1—O6^ii	2.004 (3)	P4—O4	1.484 (4)
V1—O3^iii	2.006 (3)	P4—O5	1.505 (4)
V1—O5	2.007 (3)	P4—H4A	1.38 (6)
V2—O4^iv	1.976 (3)	P4—H4B	1.34 (5)
V2—O12	1.984 (3)	P5—O7	1.493 (4)
V2—O11	1.990 (4)	P5—O1	1.500 (4)
V2—O10	1.996 (3)	P5—H5A	1.25 (6)
V2—O8	2.010 (4)	P5—H5B	1.36 (5)
V2—O2^v	2.023 (3)	P6—O11	1.488 (4)
P1—O8	1.488 (4)	P6—O9	1.505 (3)
P1—O2	1.504 (3)	P6—H6A	1.36 (6)
P1—H1A	1.36 (6)	P6—H6B	1.32 (5)
P1—H1B	1.43 (5)	O1—V1^vi	1.991 (3)
P2—O3	1.504 (3)	O2—V2^vii	2.023 (3)
P2—O10	1.508 (3)	O3—V1^viii	2.006 (3)
P2—H2A	1.42 (5)	O4—V2^ix	1.976 (3)
P2—H2B	1.43 (5)	O6—V1^x	2.004 (3)
P3—O12	1.495 (4)
O7—V1—O1^i	177.79 (15)	O3—P2—H2B	106 (2)
O7—V1—O9	90.39 (15)	O10—P2—H2B	110 (2)
O1^i—V1—O9	87.82 (14)	H2A—P2—H2B	99 (3)
O7—V1—O6^ii	90.56 (15)	O12—P3—O6	114.1 (2)
O1^i—V1—O6^ii	90.71 (15)	O12—P3—H3A	112 (2)
O9—V1—O6^ii	89.14 (14)	O6—P3—H3A	103 (2)
O7—V1—O3^iii	88.90 (14)	O12—P3—H3B	113 (2)
O1^i—V1—O3^iii	89.90 (14)	O6—P3—H3B	106 (2)
O9—V1—O3^iii	93.05 (14)	H3A—P3—H3B	108 (3)
O6^ii—V1—O3^iii	177.75 (15)	O4—P4—O5	116.8 (2)
O7—V1—O5	92.36 (15)	O4—P4—H4A	103 (2)
O1^i—V1—O5	89.51 (15)	O5—P4—H4A	109 (2)
O9—V1—O5	175.46 (15)	O4—P4—H4B	121 (2)
O6^ii—V1—O5	87.22 (13)	O5—P4—H4B	104 (2)
O3^iii—V1—O5	90.62 (14)	H4A—P4—H4B	102 (3)
O4^iv—V2—O12	89.79 (17)	O7—P5—O1	116.4 (2)
O4^iv—V2—O11	176.70 (17)	O7—P5—H5A	117 (3)
O12—V2—O11	87.77 (16)	O1—P5—H5A	111 (3)
O4^iv—V2—O10	92.31 (16)	O7—P5—H5B	113 (2)
O12—V2—O10	177.05 (15)	O1—P5—H5B	114 (2)
O11—V2—O10	90.21 (16)	H5A—P5—H5B	81 (3)
O4^iv—V2—O8	90.13 (16)	O11—P6—O9	115.2 (2)
O12—V2—O8	90.02 (15)	O11—P6—H6A	112 (2)
O11—V2—O8	92.08 (18)	O9—P6—H6A	108 (2)
O10—V2—O8	87.90 (14)	O11—P6—H6B	113 (2)
O4^iv—V2—O2^v	87.75 (14)	O9—P6—H6B	107 (2)
O12—V2—O2^v	92.00 (15)	H6A—P6—H6B	100 (3)
O11—V2—O2^v	90.13 (17)	P5—O1—V1^vi	136.4 (2)
O10—V2—O2^v	90.16 (14)	P1—O2—V2^vii	138.6 (2)
O8—V2—O2^v	177.06 (15)	P2—O3—V1^viii	135.3 (2)
O8—P1—O2	115.8 (2)	P4—O4—V2^ix	140.5 (2)
O8—P1—H1A	111 (2)	P4—O5—V1	132.7 (2)
O2—P1—H1A	105 (2)	P3—O6—V1^x	135.8 (2)
O8—P1—H1B	107 (2)	P5—O7—V1	132.1 (2)
O2—P1—H1B	115 (2)	P1—O8—V2	137.1 (2)
H1A—P1—H1B	103 (3)	P6—O9—V1	137.1 (2)
O3—P2—O10	117.3 (2)	P2—O10—V2	131.1 (2)
O3—P2—H2A	113 (2)	P6—O11—V2	136.0 (3)
O10—P2—H2A	110 (2)	P3—O12—V2	135.4 (2)

Symmetry codes: (i) −x+1/2, y−1/2, −z+3/2; (ii) x−1/2, −y+1/2, z+1/2; (iii) x+1/2, −y+1/2, z+1/2; (iv) x, y, z−1; (v) −x+1/2, y+1/2, −z+1/2; (vi) −x+1/2, y+1/2, −z+3/2; (vii) −x+1/2, y−1/2, −z+1/2; (viii) x−1/2, −y+1/2, z−1/2; (ix) x, y, z+1; (x) x+1/2, −y+1/2, z−1/2.