Hydrothermally synthesized dipotassium gallium {hydrogen bis[hydrogenphosphate(V)]} difluoride, K
2Ga[H(HPO
4)
2]F
2, is isotypic with K
2Fe[H(HPO
4)
2]F
2. The main features of the structure are ([Ga{H(HPO
4)
2}F
2]
2−)
n columns consisting of centrosymmetric Ga(F
2O
4) octahedra [average Ga—O = 1.966 (3) Å and Ga—F = 1.9076 (6) Å] stacked above two HPO
4 tetrahedra [average P—O = 1.54 (2) Å] sharing two O-atom vertices. The charge-balancing seven-coordinate K
+ cations [average K—O,F = 2.76 (2) Å] lie in the intercolumn space, stabilizing a three-dimensional structure. Strong [O
O = 2.4184 (11) Å] and medium [O
F = 2.6151 (10) Å] hydrogen bonds further reinforce the connections between adjacent columns.
Supporting information
Compound (I) was prepared hydrothermally from a mixture of Ga2O3 (0.607 g),
KH2PO4 (3.081 g), H3PO4 (2.13 ml of an 85% solution), HF (0.65 ml of a
19% solution) and deionized water, corresponding to a K:Ga:P:F =
3.5:1:5:2 starting ratio. These components were sealed in a 15 ml Teflon-lined
autoclave filled to approximately 75% of its capacity and then heated to 473 K
for 96 h under autogenous pressure. The pH was roughly equal to 1.0 during the
synthesis. After cooling to room temperature, the solid product was filtered
off, washed with water, rinsed with ethanol and then dried in air. It
consisted of colourless transparent needle-like [`pseudo cubic' in CIF]
crystals of (I) and some polycrystalline material. The presence of K, Ga, P
and F in the crystals was confirmed by quantitative energy-dispersive X-ray
analysis. Powder X-ray diffraction analysis of the reaction products revealed
the cocrystallization of two phases: K2Ga[H(HPO4)2]F2 (~40 vol%)
and KGaF1 - x(OH)xPO4 (~60 vol%). The selected
crystal of (I) was bounded by a {011} prism, an incomplete {311} prism and
a (112) bevel face.
The atomic coordinates of isotypic K2Fe[H(HPO4)2]F2 (Mi et al.,
2005) were used as starting parameters in the final refinement. The H atoms
were refined with fixed isotropic displacement parameters. The highest
electron-density peak is 1.92 Å from the H1 site.
Data collection: X-AREA (Stoe & Cie, 2006); cell refinement: X-AREA???; data reduction: X-RED (Stoe & Cie, 2005); program(s) used to solve structure: SIR02 (Burla et al., 2003); program(s) used to refine structure: JANA2000 (Petříček et al., 2000); molecular graphics: DIAMOND (Brandenburg, 1999 or 2001?); software used to prepare material for publication: JANA2000.
dipotassium gallium {hydrogen bis[hydrogenphosphate(V)]} difluoride
top
Crystal data top
K2Ga[H(HPO4)2]F2 | F(000) = 368 |
Mr = 378.9 | Dx = 2.958 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 24572 reflections |
a = 4.7449 (6) Å | θ = 4.3–38.3° |
b = 8.2814 (8) Å | µ = 4.65 mm−1 |
c = 10.8351 (13) Å | T = 293 K |
β = 92.941 (10)° | Pseudo cubic, colourless |
V = 425.20 (8) Å3 | 0.13 × 0.13 × 0.12 mm |
Z = 2 | |
Data collection top
STOE IPDS II diffractometer | 1824 independent reflections |
Radiation source: fine-focus sealed tube | 1768 reflections with I > 3σ(I) |
Graphite monochromator | Rint = 0.024 |
Detector resolution: 6.67 pixels mm-1 | θmax = 38.9°, θmin = 4.3° |
rotation method scans | h = −8→8 |
Absorption correction: integration X-RED (Stoe & Cie, 2005) | k = −13→14 |
Tmin = 0.468, Tmax = 0.644 | l = −18→18 |
11412 measured reflections | |
Refinement top
Refinement on F | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.016 | Hydrogen site location: difference Fourier map |
wR(F2) = 0.033 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.23 | Weighting scheme based on measured s.u.'s w = 1/[σ2(F) + 0.000625F2] |
1824 reflections | (Δ/σ)max = 0.001 |
77 parameters | Δρmax = 0.35 e Å−3 |
0 restraints | Δρmin = −0.33 e Å−3 |
0 constraints | Extinction correction: B-C type 1 Gaussian isotropic
[Becker, P. J. & Coppens, P. (1974). Acta Cryst. A30, 129–153] |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0042 (4) |
Crystal data top
K2Ga[H(HPO4)2]F2 | V = 425.20 (8) Å3 |
Mr = 378.9 | Z = 2 |
Monoclinic, P21/c | Mo Kα radiation |
a = 4.7449 (6) Å | µ = 4.65 mm−1 |
b = 8.2814 (8) Å | T = 293 K |
c = 10.8351 (13) Å | 0.13 × 0.13 × 0.12 mm |
β = 92.941 (10)° | |
Data collection top
STOE IPDS II diffractometer | 1824 independent reflections |
Absorption correction: integration X-RED (Stoe & Cie, 2005) | 1768 reflections with I > 3σ(I) |
Tmin = 0.468, Tmax = 0.644 | Rint = 0.024 |
11412 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.016 | 0 restraints |
wR(F2) = 0.033 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.23 | Δρmax = 0.35 e Å−3 |
1824 reflections | Δρmin = −0.33 e Å−3 |
77 parameters | |
Special details top
Refinement. Friedel pairs have been merged |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Ga1 | 0.5 | 0.5 | 0.5 | 0.00634 (5) | |
K1 | 0.50416 (5) | 0.09965 (3) | 0.33230 (2) | 0.01614 (7) | |
P1 | 0.01485 (4) | 0.26253 (3) | 0.58517 (2) | 0.00680 (7) | |
F1 | 0.32320 (13) | 0.40952 (8) | 0.35374 (6) | 0.01161 (14) | |
O1 | −0.24822 (15) | 0.31059 (9) | 0.50932 (7) | 0.01073 (16) | |
O2 | 0.23576 (15) | 0.39271 (9) | 0.60658 (7) | 0.01034 (16) | |
O3 | 0.15181 (16) | 0.11252 (9) | 0.52894 (9) | 0.01435 (18) | |
O4 | −0.09342 (17) | 0.21143 (12) | 0.71591 (8) | 0.0166 (2) | |
H1 | 0.025 (5) | 0.166 (3) | 0.764 (3) | 0.035* | |
H2 | 0.059 (12) | 0.051 (8) | 0.509 (5) | 0.035* | 0.5 |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Ga1 | 0.00602 (9) | 0.00642 (9) | 0.00643 (10) | −0.00058 (3) | −0.00116 (6) | −0.00051 (3) |
K1 | 0.01872 (11) | 0.01775 (12) | 0.01182 (12) | 0.00461 (7) | −0.00052 (8) | −0.00101 (7) |
P1 | 0.00568 (11) | 0.00597 (11) | 0.00871 (12) | 0.00003 (6) | −0.00009 (8) | 0.00102 (6) |
F1 | 0.0117 (2) | 0.0132 (3) | 0.0095 (2) | −0.00176 (18) | −0.00295 (19) | −0.00266 (19) |
O1 | 0.0092 (2) | 0.0098 (3) | 0.0128 (3) | 0.00198 (19) | −0.0037 (2) | −0.0004 (2) |
O2 | 0.0097 (2) | 0.0104 (3) | 0.0110 (3) | −0.0035 (2) | 0.0003 (2) | −0.0009 (2) |
O3 | 0.0115 (3) | 0.0075 (3) | 0.0241 (4) | 0.0019 (2) | 0.0010 (3) | −0.0039 (2) |
O4 | 0.0126 (3) | 0.0240 (4) | 0.0135 (3) | 0.0020 (3) | 0.0030 (3) | 0.0094 (3) |
Geometric parameters (Å, º) top
Ga1—F1 | 1.9079 (6) | K1—O3vi | 2.7858 (8) |
Ga1—F1i | 1.9079 (6) | K1—O4vii | 3.2562 (9) |
Ga1—O1ii | 1.9712 (7) | K1—O4viii | 2.8163 (9) |
Ga1—O1iii | 1.9712 (7) | P1—F1 | 3.2073 (7) |
Ga1—O2 | 1.9604 (7) | P1—F1iii | 3.2398 (7) |
Ga1—O2i | 1.9604 (7) | P1—O1 | 1.5121 (7) |
K1—F1 | 2.7197 (7) | P1—O2 | 1.5133 (7) |
K1—F1iv | 2.7172 (7) | P1—O3 | 1.5419 (8) |
K1—O1ii | 2.8070 (8) | P1—O4 | 1.5889 (9) |
K1—O2v | 2.6996 (8) | H1—O4 | 0.84 (3) |
K1—O3 | 2.7770 (9) | H2—O3 | 0.70 (6) |
| | | |
F1—Ga1—F1i | 180 | F1iv—K1—O3 | 143.87 (2) |
F1—Ga1—O1ii | 88.26 (3) | F1iv—K1—O3vi | 81.04 (2) |
F1—Ga1—O1iii | 91.74 (3) | F1iv—K1—O4vii | 67.87 (2) |
F1—Ga1—O2 | 92.53 (3) | F1iv—K1—O4viii | 75.67 (2) |
F1—Ga1—O2i | 87.47 (3) | O1ii—K1—O2v | 139.99 (2) |
F1i—Ga1—F1 | 180 | O1ii—K1—O3 | 72.50 (2) |
F1i—Ga1—O1ii | 91.74 (3) | O1ii—K1—O3vi | 79.08 (2) |
F1i—Ga1—O1iii | 88.26 (3) | O1ii—K1—O4vii | 145.90 (2) |
F1i—Ga1—O2 | 87.47 (3) | O1ii—K1—O4viii | 71.98 (2) |
F1i—Ga1—O2i | 92.53 (3) | O2v—K1—O3 | 114.81 (2) |
O1ii—Ga1—O1iii | 180 | O2v—K1—O3vi | 137.72 (3) |
O1ii—Ga1—O2 | 90.77 (3) | O2v—K1—O4vii | 67.82 (2) |
O1ii—Ga1—O2i | 89.23 (3) | O2v—K1—O4viii | 83.13 (2) |
O1iii—Ga1—O1ii | 180 | O3—K1—O3vi | 88.24 (3) |
O1iii—Ga1—O2 | 89.23 (3) | O3—K1—O4vii | 76.97 (2) |
O1iii—Ga1—O2i | 90.77 (3) | O3—K1—O4viii | 140.44 (3) |
O2—Ga1—O2i | 180 | O3vi—K1—O3 | 88.24 (3) |
O2i—Ga1—O2 | 180 | O3vi—K1—O4vii | 85.23 (2) |
F1—K1—F1iv | 135.94 (2) | O3vi—K1—O4viii | 101.54 (2) |
F1—K1—O1ii | 58.49 (2) | O4vii—K1—O4viii | 141.41 (3) |
F1—K1—O2v | 85.35 (2) | O4viii—K1—O4vii | 141.41 (3) |
F1—K1—O3 | 72.13 (2) | O1—P1—O2 | 116.22 (4) |
F1—K1—O3vi | 136.71 (2) | O1—P1—O3 | 110.50 (4) |
F1—K1—O4vii | 124.83 (2) | O1—P1—O4 | 105.01 (4) |
F1—K1—O4viii | 74.83 (2) | O2—P1—O3 | 109.39 (4) |
F1iv—K1—F1 | 135.94 (2) | O2—P1—O4 | 107.83 (5) |
F1iv—K1—O1ii | 137.39 (2) | O3—P1—O4 | 107.44 (5) |
F1iv—K1—O2v | 59.18 (2) | | |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) x+1, y, z; (iii) −x, −y+1, −z+1; (iv) −x+1, y−1/2, −z+1/2; (v) x, −y+1/2, z−1/2; (vi) −x+1, −y, −z+1; (vii) −x, −y, −z+1; (viii) x+1, −y+1/2, z−1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H1···F1ix | 0.84 (3) | 1.79 (3) | 2.6151 (10) | 170 (3) |
O3—H2···O3vii | 0.70 (6) | 1.72 (6) | 2.4185 (11) | 174 (7) |
Symmetry codes: (vii) −x, −y, −z+1; (ix) x, −y+1/2, z+1/2. |
Experimental details
Crystal data |
Chemical formula | K2Ga[H(HPO4)2]F2 |
Mr | 378.9 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 293 |
a, b, c (Å) | 4.7449 (6), 8.2814 (8), 10.8351 (13) |
β (°) | 92.941 (10) |
V (Å3) | 425.20 (8) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 4.65 |
Crystal size (mm) | 0.13 × 0.13 × 0.12 |
|
Data collection |
Diffractometer | STOE IPDS II diffractometer |
Absorption correction | Integration X-RED (Stoe & Cie, 2005) |
Tmin, Tmax | 0.468, 0.644 |
No. of measured, independent and observed [I > 3σ(I)] reflections | 11412, 1824, 1768 |
Rint | 0.024 |
(sin θ/λ)max (Å−1) | 0.883 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.016, 0.033, 1.23 |
No. of reflections | 1824 |
No. of parameters | 77 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.35, −0.33 |
Selected geometric parameters (Å, º) topGa1—F1 | 1.9079 (6) | K1—O3vi | 2.7858 (8) |
Ga1—F1i | 1.9079 (6) | K1—O4vii | 3.2562 (9) |
Ga1—O1ii | 1.9712 (7) | K1—O4viii | 2.8163 (9) |
Ga1—O1iii | 1.9712 (7) | P1—F1 | 3.2073 (7) |
Ga1—O2 | 1.9604 (7) | P1—F1iii | 3.2398 (7) |
Ga1—O2i | 1.9604 (7) | P1—O1 | 1.5121 (7) |
K1—F1 | 2.7197 (7) | P1—O2 | 1.5133 (7) |
K1—F1iv | 2.7172 (7) | P1—O3 | 1.5419 (8) |
K1—O1ii | 2.8070 (8) | P1—O4 | 1.5889 (9) |
K1—O2v | 2.6996 (8) | H1—O4 | 0.84 (3) |
K1—O3 | 2.7770 (9) | H2—O3 | 0.70 (6) |
| | | |
F1—Ga1—F1i | 180 | O2—Ga1—O2i | 180 |
F1—Ga1—O1ii | 88.26 (3) | O1—P1—O2 | 116.22 (4) |
F1—Ga1—O1iii | 91.74 (3) | O1—P1—O3 | 110.50 (4) |
F1—Ga1—O2 | 92.53 (3) | O1—P1—O4 | 105.01 (4) |
F1—Ga1—O2i | 87.47 (3) | O2—P1—O3 | 109.39 (4) |
O1ii—Ga1—O1iii | 180 | O2—P1—O4 | 107.83 (5) |
O1ii—Ga1—O2 | 90.77 (3) | O3—P1—O4 | 107.44 (5) |
O1ii—Ga1—O2i | 89.23 (3) | | |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) x+1, y, z; (iii) −x, −y+1, −z+1; (iv) −x+1, y−1/2, −z+1/2; (v) x, −y+1/2, z−1/2; (vi) −x+1, −y, −z+1; (vii) −x, −y, −z+1; (viii) x+1, −y+1/2, z−1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H1···F1ix | 0.84 (3) | 1.79 (3) | 2.6151 (10) | 170 (3) |
O3—H2···O3vii | 0.70 (6) | 1.72 (6) | 2.4185 (11) | 174 (7) |
Symmetry codes: (vii) −x, −y, −z+1; (ix) x, −y+1/2, z+1/2. |
Microporous gallium phosphates have been widely studied because they find many potential applications in, for example, catalysis, ion-exchangers and adsorbents (Cheetham et al., 1999). The fluoride ion has been discovered to play a major role in the gallium phosphate system, and various series of complex fluoride gallium phosphates with organic molecules substituting for the alkali cations have been synthesized by Férey and other researchers. On the other hand, the known alkali (ammonium) fluoride gallium phosphates show considerable structural variety (LiGa3F3(OH)(H2O)2(PO4)2 (Beitone et al., 2001), LiGa(PO4)F0.74(OH)0.26 (Beitone et al., 2002), KGaF1-δ(OH)δPO4 (Harrison et al., 1995), K[(GaPO4){F0.25(GaPO4)}4] (Sun et al., 2003), (NH4)0.93(H3O)0.07Ga(PO4)(OH)0.5F0.5 (Férey et al., 1993), (NH4)Ga(PO4)F and (NH4)2Ga2(PO4)(HPO4)F3 (Loiseau et al., 2000)).
Recently, we have been systematically studying the reactivity of alkali and ammonium cations in hydrothermal synthesis and the crystal chemistry of complex gallium and indium phosphates without fluoride agents (Filaretov, Zhizhin, Komissarova et al., 2002; Zhizhin et al., 2000; Filaretov et al., 2006; Rusakov et al., 2006) and with fluoride ions as templates (Filaretov, Zhizhin, Olenev et al., 2002; Komissarova et al., 2002). In this context, we report here the hydrothermal synthesis and characterization of the first potassium gallium hydrogenphosphate fluoride, K2Ga[H(HPO4)2]F2, (I).
The crystal structure of (I) belongs to the K2Fe[H(HPO4)2]F2 structure type (Mi et al., 2005). The asymmetric unit contains four O, two H and one each of K, Ga, P and F atoms. The structure can be described as negatively charged infinite {[Ga[H(HPO4)2]F2]2-}n columns extending along [100]. The columns are built of corner-sharing Ga[F2O4] octahedra and tetrahedral HPO4 units fused together via Ga—O—P bonds (Figs. 1 and 2). Each Ga[F2O4] octahedron shares two of its four O vertices with two adjacent phosphate tetrahedra, while each HPO4 tetrahedron links two of its non-hydroxy O vertices to two Ga[F2O4] octahedra. The charge-balancing K+ cations are located in the space between the columns, thus completing a three-dimensional structure. Additional sturdiness of the structure, i.e. reinforcement of the connections between adjacent columns, is provided by two hydrogen bonds.
According to the narrow range of K—O and K—F distances, the K+ cation (site symmetry 1) adopts a sevenfold coordination comprising two F and five O nearest neighbours, with an average K—O,F bond length of 2.76 (2) Å. The bond valence sum (BVS) of 1.16 for K calculated by the Brese & O'Keeffe (1991) formalism shows that its valence requirement is satisfied by this coordination. However, this coordination number is not unique because the outer O4 atom {as in K2Fe[H(HPO4)2]F2; Fig. 2 of Mi et al. (2005)} might or might not be part of the coordination environment to 3.2562 (9) Å. If it is included, the BVS value of the [7 + 1]-coordinate K+ cation rises to 1.21, but this coordination still agrees with the maximum gap in the K—O distance, assuming a cut-off of 3.35 Å (Donnay & Allmann, 1970). The ninth O neighbour at 3.4222 (9) Å is clearly beyond this cut-off (Table 1). The coordination environment of the K+ cation is so asymmetric that no easy polyhedral description can be proposed.
As shown by the Ga—O and Ga—F distances (Table 1), the Ga3+ cation (site symmetry 1) is characterized by a typical and nearly regular octahedral geometry (Harrison et al., 1995; Loiseau et al., 2000; Beitone et al., 2002; Filaretov et al., 2006; Rusakov et al., 2006) with four long equatorial Ga—O bonds and two slightly shorter Ga—F bonds. The BVS value of 3.03 for Ga agrees with that expected for trivalent gallium. The P atom reveals its normal tetrahedral coordination [average P—O = 1.54 (2) Å] and participates in P—O1—Ga, P—O2—Ga and two terminal P—O bonds. The BVS of P is unexceptional (4.79, expected 5.00). On the basis of its length, the P—O4 bond is assumed to be protonated. The BVS values for O1 (1.96), O2 (2.03), O3 (1.54) and O4 (1.28) are all reasonably close to expected ideal valences and confirm that atoms O3 and O4 represent hydroxy groups. Atoms O4 and H1, both in general positions, participate in a moderately strong O4—H1 ··· F hydrogen bond (Table 2). In contrast, the P—O3 distance (Table 1) is typical for P—O distances in PO4 tetrahedra. This is so because O3 is involved in a very short symmetry-restricted hydrogen bond (Table 2).
A difference electron-density map calculated after full-matrix least-squares refinement including all non-H atoms with anisotropic displacement parameters clearly shows a maximum near O4 between O4 and F (interpreted as atom H1) and two maxima close to the inversion centre at (0,1/2,0) between two O3 atoms related by inversion (Fig. 3). These two maxima were suggestive of disordered hydrogen positions and were therefore refined with a fixed isotropic displacement parameter and a half occupancy. This kind of disordered hydrogen is characteristic of the K2Fe[H(HPO4)2]F2 and Li2Fe[(PO4)(HPO4)] structures (Mi et al., 2004). One might suspect that the structural formula Li2Fe[(PO4)(HPO4)] does not take into account the fact that the H atom is shared between two structurally identical P sites. Probably, a more correct formula should read Li2Fe[H(PO4)2], or as a new Sc analogue, Li2Sc[H(PO4)2] according to recent results of ours. The crystal chemical function of the H2 atoms is to interconnect the {[Ga[H(HPO4)2]F2]2-}n columns in the ab plane (Fig. 3). Similarly, very short symmetry-restricted hydrogen bonds are well known and have recently been reported for structures of hydrogenphosphates, arsenates and borates (Mi et al., 2004; Schwendtner & Kolitsch, 2005; Massa et al., 2006). They were also found in the novel hydrogenphosphates Li2Sc[H(PO4)2] and Ba4Sc2[H(PO4)2](HPO4)4(H2PO4)·2H2O (Filaretov et al., unpublished results).
In conclusion, the K2Ga[H(HPO4)2]F2 structure reveals an original arrangement which had not yet been found amongst well known complex gallium phosphates.