Dipotassium trizirconium oxide dodecafluoride, K
2Zr
3OF
12, obtained by microwave-assisted hydrothermal synthesis, crystallizes in the trigonal space group
Rm (No. 166) and is isostructural with Tl
2Zr
3OF
12. The structure was determined from X-ray powder diffraction data and is described in terms of fluorine- or oxygen-centered cation polyhedra and consists of [F
12O
2KZr
6]
∞ and [F
12K
3Zr
6]
∞ layers connected by Zr
4+ cations.
Supporting information
Key indicators
- Powder X-ray study
- T = 293 K
- R factor = 0.000
- wR factor = 0.000
- Data-to-parameter ratio = 18.1
checkCIF/PLATON results
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A powder sample of K2Zr3OF12 was prepared from 0.6688 g of ZrF4 and 10 ml of a 0.4 M KOH solution. The reaction mixture was then heated for 1 h at T = 463 K (P = 12 10 5 Pa) in a CEM microwave oven (MDS 2100) using a Teflon-lined autoclave. The compound was then washed with acetone and dried in air. The product was characterized by X-ray powder diffraction on a Siemens Brucker D8 diffractometer. Thermal analysis was performed with a DTA–TGA TA Instrument 260 (heating rate 10 K min−1; argon atmosphere). Above 908 K, K2Zr3OF12 decomposes and undergoes hydrolysis to give ZrO2 and K3ZrF7. Owing to the absence of IR lines around 3300 and 1600 cm−1, the F−–OH− substitution, expected from the preparation mode, is excluded.
Reflection positions were determined by means of the EVA program (available in the Socabim PC software package DIFFRAC-AT supplied by Siemens, derivative method) after Kα2 radiation stripping. Auto-indexing of 13 intense reflections by using the McMaille program (Le Bail, 2002) leads to an hexagonal cell similar to that of Tl2Zr3OF12. The atomic positions of Tl2Zr3OF12 were used as a starting model.
Program(s) used to refine structure: FULLPROF (Rodriguez-Carvajal, 1998); molecular graphics: DIAMOND (Brandenburg, 2001); software used to prepare material for publication: FULLPROF (Rodriguez-Carvajal, 1998).
Zirconium potassium oxide fluoride
top
Crystal data top
K2Zr3OF12 | Z = 6 |
Mr = 595.85 | F(000) = 1638 |
Trigonal, R3m | Dx = 4.016 Mg m−3 |
Hall symbol: -R 3 2" | Cu Kα radiation, λ = 1.54178 Å |
a = 7.6887 (3) Å | T = 293 K |
c = 28.870 (1) Å | white |
V = 1478.0 (2) Å3 | ?, ? × ? × ? mm |
Data collection top
D8 Bruker diffractometer | Scan method: step |
None monochromator | 2θmin = 11°, 2θmax = 100°, 2θstep = 0.02° |
Specimen mounting: packed powder pellet | |
Refinement top
Refinement on Inet | Excluded region(s): 5.00 → 11.00° |
Rp = 0.12 | Profile function: pseudo-Voigt |
Rwp = 0.139 | 26 parameters |
Rexp = 0.057 | 0 restraints |
RBragg = 0.066 | 0 constraints |
χ2 = 5.905 | |
4751 data points | Background function: linear interpolation |
Crystal data top
K2Zr3OF12 | V = 1478.0 (2) Å3 |
Mr = 595.85 | Z = 6 |
Trigonal, R3m | Cu Kα radiation, λ = 1.54178 Å |
a = 7.6887 (3) Å | T = 293 K |
c = 28.870 (1) Å | ?, ? × ? × ? mm |
Data collection top
D8 Bruker diffractometer | Scan method: step |
Specimen mounting: packed powder pellet | 2θmin = 11°, 2θmax = 100°, 2θstep = 0.02° |
Refinement top
Rp = 0.12 | χ2 = 5.905 |
Rwp = 0.139 | 4751 data points |
Rexp = 0.057 | 26 parameters |
RBragg = 0.066 | 0 restraints |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
K1 | 0 | 0 | 0 | 0.021 (1)* | |
K2 | 0 | 0 | 0.5 | 0.021 (1)* | |
K3 | 0 | 0 | 0.1364 (2) | 0.0211 (11)* | |
Zr | 0.51535 (9) | −0.51535 (9) | 0.06227 (5) | 0.0110 (4)* | |
F1 | 0.3376 (7) | 0 | 0 | 0.0129 (9)* | |
F2 | 0.1473 (4) | −0.1473 (4) | 0.2019 (2) | 0.0129 (9)* | |
F3 | 0.1574 (4) | −0.1574 (4) | 0.9233 (2) | 0.0129 (9)* | |
F4 | 0.2214 (4) | −0.2214 (4) | 0.0727 (2) | 0.0129 (9)* | |
O | 0 | 0 | 0.2830 (4) | 0.0129 (9)* | |
Geometric parameters (Å, º) top
K1—F1i | 2.595 (5) | Zr—Ov | 2.044 (2) |
K2—F2ii | 2.679 (4) | Zr—F4v | 2.139 (3) |
K3—F3iii | 2.711 (5) | Zr—F4vi | 2.139 (3) |
K3—F2iv | 2.726 (6) | Zr—F1vii | 2.198 (2) |
K3—F2 | 2.726 (6) | Zr—F1vi | 2.198 (2) |
Zr—F2v | 1.997 (6) | Zr—F3viii | 2.237 (3) |
Zr—Ov | 2.044 (2) | Zr—F3ix | 2.237 (3) |
Zr—Ov | 2.044 (2) | | |
| | | |
F1—K1—F3 | 126.69 (12) | F2—Zr—O | 99.1 (4) |
F1—K1—F3 | 90.0 | F2—Zr—F4 | 82.5 (2) |
F3—K1—F3 | 106.6 (2) | O—Zr—F4 | 143.1 (2) |
F3—K1—F3 | 180.0 | F4—Zr—F4 | 73.8 (4) |
F2—K2—F2 | 106.7 (2) | F2—Zr—F1 | 145.4 (2) |
F2—K2—F4 | 123.6 (2) | O—Zr—F1 | 87.0 (3) |
F2—K2—F4 | 96.6 (2) | F4—Zr—F1 | 73.1 (2) |
F4—K2—F4 | 180.000 (1) | F4—Zr—F1 | 112.5 (2) |
F4—K2—F4 | 130.7 (2) | F1—Zr—F1 | 68.3 (4) |
F4—K2—F4 | 130.7 (2) | F2—Zr—F3 | 78.5 (2) |
F4—K2—F4 | 49.3 (2) | O—Zr—F3 | 69.8 (2) |
F4—K2—F4 | 130.7 (2) | F4—Zr—F3 | 144.7 (3) |
F3—K3—F3 | 84.8 (2) | F4—Zr—F3 | 74.5 (2) |
F3—K3—F2 | 175.4 (3) | F1—Zr—F3 | 134.6 (2) |
F3—K3—F2 | 98.6 (2) | F1—Zr—F3 | 71.8 (2) |
F2—K3—F2 | 77.8 (3) | F3—Zr—F3 | 129.1 (4) |
Symmetry codes: (i) −x+y, −x, z; (ii) x−y−2/3, x−1/3, −z+2/3; (iii) y, −x+y, −z+1; (iv) −y, x−y, z; (v) −x+2/3, −y−2/3, −z+1/3; (vi) −x+y+1, −x, z; (vii) x−y, x−1, −z; (viii) y+1, −x+y, −z+1; (ix) x−y, x−1, −z+1. |
Experimental details
Crystal data |
Chemical formula | K2Zr3OF12 |
Mr | 595.85 |
Crystal system, space group | Trigonal, R3m |
Temperature (K) | 293 |
a, c (Å) | 7.6887 (3), 28.870 (1) |
V (Å3) | 1478.0 (2) |
Z | 6 |
Radiation type | Cu Kα, λ = 1.54178 Å |
Specimen shape, size (mm) | ?, ? × ? × ? |
|
Data collection |
Diffractometer | D8 Bruker diffractometer |
Specimen mounting | Packed powder pellet |
Data collection mode | ? |
Scan method | Step |
2θ values (°) | 2θmin = 11 2θmax = 100 2θstep = 0.02 |
|
Refinement |
R factors and goodness of fit | Rp = 0.12, Rwp = 0.139, Rexp = 0.057, RBragg = 0.066, χ2 = 5.905 |
No. of data points | 4751 |
No. of parameters | 26 |
Selected bond lengths (Å) topK1—F1i | 2.595 (5) | Zr—Ov | 2.044 (2) |
K2—F2ii | 2.679 (4) | Zr—F4v | 2.139 (3) |
K3—F3iii | 2.711 (5) | Zr—F4vi | 2.139 (3) |
K3—F2iv | 2.726 (6) | Zr—F1vii | 2.198 (2) |
K3—F2 | 2.726 (6) | Zr—F1vi | 2.198 (2) |
Zr—F2v | 1.997 (6) | Zr—F3viii | 2.237 (3) |
Zr—Ov | 2.044 (2) | Zr—F3ix | 2.237 (3) |
Zr—Ov | 2.044 (2) | | |
Symmetry codes: (i) −x+y, −x, z; (ii) x−y−2/3, x−1/3, −z+2/3; (iii) y, −x+y, −z+1; (iv) −y, x−y, z; (v) −x+2/3, −y−2/3, −z+1/3; (vi) −x+y+1, −x, z; (vii) x−y, x−1, −z; (viii) y+1, −x+y, −z+1; (ix) x−y, x−1, −z+1. |
Because of their potential activity in non-linear optics or catalysis, attention has been paid recently to fluoride salts, fluoride borates (Becker, 1998; Dorozhkin et al., 1981), fluoride carbonates (Mercier et al., 1997), fluoride sulfates (Wickleder, 1999), fluoride phosphates (Zhizhin et al., 2001). The object of our work was to investigate the crystallization of zirconium fluoride silicates from hydrothermal solutions under microwave heating. No fluoride silicate was found in the KOH–SiO2–ZrF4–H2O system and only one oxide fluoride was obtained. This phase, K2Zr3OF12, is isostructural with both Tl2Zr3OF12 (Mansouri & Avignant, 1984) and Rb2Zr3OF12 (Koller & Muller, 2002). The structure of K2Zr3OF12 was determined by powder diffraction. The X-ray diffraction pattern is given Fig. 1. Calculated bond valences (Brese & O'Keeffe, 1991) show that the interatomic distances are satisfactory and in agreement with bibliographic data. The isotropic atomic displacement parameters are also acceptable. The structure of K2Zr3OF12 consists of ZrOF7 and KF6 polyhedra. O atoms lie at the common vertex of three edge-sharing ZrOF7 polyhedra. These polyhedra, linked by corners or edges, build hexameric Zr3OF18 units which share edges in order to form [Zr6O4F30] polyanions. The polyanions, linked by corners, build infinite [ZrOF12] double layers running perpendicular to the c axis. The structure can be also described in terms of fluorine- or oxygen-centered cation polyhedra (Fig. 2a). In K2Zr3OF12, the F4 atoms adopt a twofold coordination. All other F atoms, together with O atoms, are in a triangular environment and form [FK2Zr], [FKZr2] and [OZr3] entities. The triangular groups [F1KZr2] (green), sharing Zr–Zr edges, form [F1KZr]2 dimers. These dimers, connected by K atoms, build infinite chains along the [100], [010] and [110] directions. The resulting [F16KZr6]∞ layers (Fig. 2 b) include F4 and O atoms, which form [F43Zr3] triangular cycles and [OZr3] triangular entities (red) (Fig. 2c); they build [F16F46O2Zr6K1]∞ layers perpendicular to the c axis. [F2K2K3Zr] and [F3K3Zr2] entities, purple and yellow, respectively, are linked by corners and define cages of six triangles (4 × F2 and 2 × F3). These cages, connected one to each other, build [F26F36K3Zr6]∞ layers parallel to the ab plane (Fig. 2 d). The [F16F46O2Zr6K]∞ and [F26F36K3Zr6]∞ sheets which alternate along the c direction, are linked through Zr atoms.