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The title compound, K2[VF5(H2O)], was synthesized from potassium antimony tartrate, piperazine, V2O5 and HF under hydro­thermal conditions. It is isostructural with K2[FeF5(H2O)] and contains polymeric anion chains held together by strong O—H...F bonds. Each V atom is coordinated to five terminal F atoms and the O atom of one water mol­ecule. Pairs of O—H...F bonds are formed by two cis-related F atoms. Twofold axes run along the O—V—F axis of the V-centred otahedra.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103026994/iz1034sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270103026994/iz1034Isup2.hkl
Contains datablock I

Comment top

Members of the K2MF6 series have been well studied and have been found to adopt structures similar to K2PtCl6, with virtually ideal octahedral arrangements of F atoms around the metal atom (Wyckoff, 1951). For compounds of the K2MF5(H2O) series, previous researchers initially expected to obtain distinct [MF5(H2O)]2− anions in the crystal, deeming the water molecules to be part of the anion. However, studies of K2AlF5(H2O) (Wyckoff, 1951) and K2MnF5(H2O) (Edwards, 1971a) indicated that there are no separate [MF5(H2O)]2− anions. The water molecule is not part of the anion. The trivalent cation is octahedrally coordinated by bridging trans F atoms, thus forming polymeric MF6 anion chains. In this paper, we report the hydrothermal synthesis and crystal structure of the title compound, K2[VF5(H2O)], which is found to be isostructural with K2[FeF5(H2O)] (Edwards, 1971b). In the title? compound, separate [MF5(H2O)]2− anions do exist. The water molecule is part of the anion and forms strong O—H···F bonds between two anions. The structural arrangement is shown in Fig. 1. The V atom is octahedrally coordinated by five F atoms and one water molecule. There are three terminal F atoms in each octahedron, with two others (F3) forming O—H···F bonds (O—H···F =2.565 Å and θ=170.39°) configured as kinked anion chains parallel to the c axis. The K ions `fill' the inter-ion space formed by the anions. There are three types of V—F bonds. In the shorter V—F1 bond (1.9083 Å), the F atom is trans with respect to the O atom, while in the longer V—F2 bond (1.9538 Å), the F atom is cis with respect to the O atom. The three terminal V—F bonds differ in length from the analogous Fe—F bonds in K2[FeF5(H2O)], while the 1.9250 Å V—F3 bond ?is intermediate in length? between the V—F1 and V—F2 bonds because of the effect of O—H···F bonds.

Unfortunately, no examples of distinct [VF6]3− octahedra that are directly comparable to the aqua complex have been identified. However VF3(H2O)3 (Mootz & Schwarz, 1991) and Na3V2(PO4)2F3 (Le Meins et al., 1999), which have been well characterized, have V—F bond lengths of 1.933 and 1.881 Å, respectively, differing slightly from those reported here.

In (NH4)2[VF4O] (Bukovec & Golic, 1980), because of the effect ?of the presence of? ammonium, the terminal V—F bond lengths are of unequal lengths. The difference between the lengths of the two bridging V—F bonds is that one is cis and the other is trans with respect to the O atom. Waltersson (1979) discussed different metal–ligand effects and considered that the trans effect plays an important role in differences in the V—F bond length. We therefore suspect that the trans effect plays an appreciable role governing the V—F bond lengths in K2[VF5(H2O)]

In the V-centred octahedra, the V—O bond lengths (2.0663 Å) are similar to the Fe—O bond length in K2[FeF5(H2O)] but longer than the V—O bond length in VF3(H2O)3 [1.985 (4) Å]. In K2[FeF5(H2O)], the author assessed the effect of the water molecule on the five-coordinate species and concluded that the water molecule has an appreciable effect on the ligand(apical)–M–ligand(basal) bond angles.

In the title compound, although the V—O bond length is so long that the V—O bond order is feeble, this bond affects the ligand–M–ligand angles, which are different from those in VF3(H2O)3 [the Fapical–V–Fbasal angles F—V—O and O—V—F are 92.9, 88.5 and 177.9°, respectively). The F—V—F and F—V—O angles of the title compound are listed in Table 3. The F—O bond length is 2.565 Å and these atoms are associated with a hydrogen bond.

The structural arrangement of the chain is shown in Fig. 2. Two anions [VF5(H2O)]2− have C2 symmetry; two F3 atoms that are cis with respect to the O atom form O—H···F bonds, giving a kinked chain along the c axis.

Experimental top

The title compound was prepared hydrothermally from a mixture of V2O5(0.5 mmol), potassium antimony tartrate (1 mmol), pipe (piperazine) (1M, 2 ml), HF (10 mmol) and H2O(6 ml), with a V:K:pipe:HF:H2O ratio of 1:1:2:10: 555 and a total volume of 10 ml. All compounds were of AR grade and were used without further purification. The mixture was stirred for about 30 min and then transferred to a 23 ml PTEF bottle, which was heated to 423 K for 2 d. Light-green crystals of the title compound were obtained in about 50% yield.

Refinement top

The positional parameters of the H atoms were fixed at positions found from difference Fourier maps.

Computing details top

Data collection: SMART (Siemens,1996); cell refinement: SMART; data reduction: SMART and SAINTS (Siemens,1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXL/PC(Sheldrick, 1993); software used to prepare material for publication: SHELXL97/2 (Sheldrick,1997).

Figures top
[Figure 1] Fig. 1. The structure of the chain in the title compound, viewed along the a axis, with displacement ellipsoids at the 50% probability level.
[Figure 2] Fig. 2. The crystal packing of (I), with displacement ellipsoids at the 50% probability level.
(I) top
Crystal data top
K2[VF5(H2O)]F(000) = 464
Mr = 242.16Dx = 2.635 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71069 Å
Hall symbol: -C 2ycCell parameters from 25 reflections
a = 9.7328 (10) Åθ = 12–18°
b = 7.9105 (6) ŵ = 3.01 mm1
c = 7.9803 (7) ÅT = 293 K
β = 96.578 (4)°Block, green
V = 610.37 (9) Å30.20 × 0.20 × 0.20 mm
Z = 4
Data collection top
Rigaku Rapid
diffractometer
701 independent reflections
Radiation source: rotor target651 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.000
ω scansθmax = 27.5°, θmin = 3.3°
Absorption correction: empirical
?
h = 012
Tmin = 0.537, Tmax = 0.548k = 010
701 measured reflectionsl = 1010
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.020Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.054H-atom parameters not refined
S = 1.11 w = 1/[σ2(Fo2) + (0.0296P)2 + 0.3825P]
where P = (Fo2 + 2Fc2)/3
701 reflections(Δ/σ)max < 0.001
44 parametersΔρmax = 0.46 e Å3
0 restraintsΔρmin = 0.27 e Å3
Crystal data top
K2[VF5(H2O)]V = 610.37 (9) Å3
Mr = 242.16Z = 4
Monoclinic, C2/cMo Kα radiation
a = 9.7328 (10) ŵ = 3.01 mm1
b = 7.9105 (6) ÅT = 293 K
c = 7.9803 (7) Å0.20 × 0.20 × 0.20 mm
β = 96.578 (4)°
Data collection top
Rigaku Rapid
diffractometer
701 independent reflections
Absorption correction: empirical
?
651 reflections with I > 2σ(I)
Tmin = 0.537, Tmax = 0.548Rint = 0.000
701 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0200 restraints
wR(F2) = 0.054H-atom parameters not refined
S = 1.11Δρmax = 0.46 e Å3
701 reflectionsΔρmin = 0.27 e Å3
44 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
V10.00000.20317 (5)0.25000.01850 (13)
K10.19914 (4)0.49683 (5)0.46967 (5)0.02822 (13)
F10.00000.45016 (18)0.25000.0266 (3)
F20.18529 (11)0.19759 (14)0.19370 (15)0.0328 (3)
F30.07033 (12)0.20360 (13)0.48550 (13)0.0317 (3)
O10.00000.0580 (2)0.25000.0454 (6)
H10.02340.11730.33260.047 (7)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
V10.0230 (2)0.0177 (2)0.0155 (2)0.0000.00559 (14)0.000
K10.0302 (2)0.0254 (2)0.0295 (2)0.00075 (13)0.00540 (16)0.00217 (14)
F10.0327 (7)0.0189 (6)0.0289 (7)0.0000.0068 (6)0.000
F20.0276 (5)0.0351 (6)0.0376 (6)0.0058 (4)0.0124 (4)0.0078 (5)
F30.0441 (6)0.0311 (6)0.0195 (5)0.0062 (4)0.0025 (4)0.0020 (4)
O10.0901 (17)0.0195 (9)0.0335 (11)0.0000.0370 (11)0.000
Geometric parameters (Å, º) top
V1—F2i1.9083 (10)K1—F1iv2.8184 (5)
V1—F21.9083 (10)K1—F2vii2.8408 (12)
V1—F31.9250 (10)K1—O1vii3.2649 (6)
V1—F3i1.9250 (10)K1—V1vii3.6243 (5)
V1—F11.9538 (14)K1—V1iv3.6606 (5)
V1—O12.066 (2)K1—K1iv3.8515 (9)
V1—K13.6063 (5)F1—K1i2.7830 (5)
V1—K1i3.6063 (5)F1—K1iv2.8184 (5)
V1—K1ii3.6243 (5)F1—K1v2.8184 (5)
V1—K1iii3.6243 (5)F2—K1viii2.6995 (12)
V1—K1iv3.6606 (5)F2—K1i2.7133 (12)
V1—K1v3.6606 (5)F2—K1iii2.8408 (12)
K1—F3iv2.6856 (11)F3—K1iv2.6856 (11)
K1—F2vi2.6995 (12)F3—K1iii2.7911 (12)
K1—F2i2.7133 (12)O1—K1ii3.2649 (5)
K1—F12.7830 (5)O1—K1iii3.2649 (5)
K1—F3vii2.7911 (12)
F2i—V1—F2177.35 (7)O1—V1—K1ii63.234 (8)
F2i—V1—F390.58 (5)K1—V1—K1ii94.347 (9)
F2—V1—F389.43 (5)K1i—V1—K1ii120.292 (12)
F2i—V1—F3i89.43 (5)F2i—V1—K1iii127.49 (4)
F2—V1—F3i90.58 (5)F2—V1—K1iii50.99 (3)
F3—V1—F3i179.80 (7)F3—V1—K1iii49.56 (4)
F2i—V1—F191.33 (3)F3i—V1—K1iii130.56 (3)
F2—V1—F191.33 (3)F1—V1—K1iii116.766 (8)
F3—V1—F189.90 (3)O1—V1—K1iii63.234 (8)
F3i—V1—F189.90 (3)K1—V1—K1iii120.292 (12)
F2i—V1—O188.67 (3)K1i—V1—K1iii94.347 (9)
F2—V1—O188.67 (3)K1ii—V1—K1iii126.467 (16)
F3—V1—O190.10 (3)F2i—V1—K1iv108.64 (3)
F3i—V1—O190.10 (3)F2—V1—K1iv73.17 (4)
F1—V1—O1180.0F3—V1—K1iv45.42 (3)
F2i—V1—K147.58 (3)F3i—V1—K1iv134.40 (4)
F2—V1—K1134.78 (4)F1—V1—K1iv49.586 (8)
F3—V1—K171.04 (4)O1—V1—K1iv130.414 (8)
F3i—V1—K1108.82 (3)K1—V1—K1iv64.007 (13)
F1—V1—K149.896 (8)K1i—V1—K1iv66.611 (9)
O1—V1—K1130.104 (8)K1ii—V1—K1iv158.351 (12)
F2i—V1—K1i134.78 (4)K1iii—V1—K1iv69.786 (11)
F2—V1—K1i47.58 (3)F2i—V1—K1v73.17 (4)
F3—V1—K1i108.82 (3)F2—V1—K1v108.64 (3)
F3i—V1—K1i71.04 (4)F3—V1—K1v134.40 (4)
F1—V1—K1i49.896 (8)F3i—V1—K1v45.42 (3)
O1—V1—K1i130.104 (8)F1—V1—K1v49.586 (8)
K1—V1—K1i99.793 (16)O1—V1—K1v130.414 (8)
F2i—V1—K1ii50.99 (3)K1—V1—K1v66.611 (9)
F2—V1—K1ii127.49 (4)K1i—V1—K1v64.007 (13)
F3—V1—K1ii130.56 (3)K1ii—V1—K1v69.786 (11)
F3i—V1—K1ii49.56 (4)K1iii—V1—K1v158.351 (12)
F1—V1—K1ii116.766 (8)K1iv—V1—K1v99.172 (16)
Symmetry codes: (i) x, y, z+1/2; (ii) x1/2, y1/2, z+1/2; (iii) x+1/2, y1/2, z; (iv) x, y+1, z+1; (v) x, y+1, z1/2; (vi) x1/2, y+1/2, z+1/2; (vii) x1/2, y+1/2, z; (viii) x+1/2, y+1/2, z1/2.

Experimental details

Crystal data
Chemical formulaK2[VF5(H2O)]
Mr242.16
Crystal system, space groupMonoclinic, C2/c
Temperature (K)293
a, b, c (Å)9.7328 (10), 7.9105 (6), 7.9803 (7)
β (°) 96.578 (4)
V3)610.37 (9)
Z4
Radiation typeMo Kα
µ (mm1)3.01
Crystal size (mm)0.20 × 0.20 × 0.20
Data collection
DiffractometerRigaku Rapid
diffractometer
Absorption correctionEmpirical
Tmin, Tmax0.537, 0.548
No. of measured, independent and
observed [I > 2σ(I)] reflections
701, 701, 651
Rint0.000
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.020, 0.054, 1.11
No. of reflections701
No. of parameters44
H-atom treatmentH-atom parameters not refined
Δρmax, Δρmin (e Å3)0.46, 0.27

Computer programs: SMART (Siemens,1996), SMART and SAINTS (Siemens,1996), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXL/PC(Sheldrick, 1993), SHELXL97/2 (Sheldrick,1997).

Selected bond angles (º) top
F2i—V1—F2177.35 (7)F3—V1—F189.90 (3)
F2i—V1—F390.58 (5)F3i—V1—F189.90 (3)
F2—V1—F389.43 (5)F2i—V1—O188.67 (3)
F2i—V1—F3i89.43 (5)F2—V1—O188.67 (3)
F2—V1—F3i90.58 (5)F3—V1—O190.10 (3)
F3—V1—F3i179.80 (7)F3i—V1—O190.10 (3)
F2i—V1—F191.33 (3)F1—V1—O1180.0
F2—V1—F191.33 (3)
Symmetry code: (i) x, y, z+1/2.
 

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