Polymorphism of NaVO₂F₂: a P2₁/c superstructure with pseudosymmetry of P2₁/m in the subcell

The ADDSYM routine in the program PLATON [Spek (2015). Acta Cryst. C71, 9-18] has helped researchers to avoid structures of (metal-)organic compounds being reported in an unnecessarily low symmetry space group. However, determination of the correct space group may get more complicated in cases of pseudosymmetric inorganic compounds. One example is NaVO₂F₂, which was reported [Crosnier-Lopez et al. (1994). Eur. J. Solid State Inorg. Chem. 31, 957-965] in the acentric space group P2₁ based on properties but flagged by ADDSYM as (pseudo)centrosymmetric P2₁/m within default distance tolerances. Herein a systematic investigation reveals that NaVO₂F₂ exists in at least four polymorphs: P2₁, (I), P2₁/m, (II), P2₁/c, (III), and one or more low-temperature ones. The new centrosymmetric modification, (III), with the space group P2₁/c has a similar atomic packing geometry to phase (I), except for having a doubled c axis. The double-cell of phase (III) arises from atomic shifts from the glide plane c at (x, , z). With increasing temperature, the number of observed reflections decreases. The odd l reflections gradually become weaker and, correspondingly, all atoms shift towards the glide plane, resulting in a gradual second-order transformation of (III) into high-temperature phase (II) (P2₁/m) at below 493 K. At least one first-order enanti­otropic phase transition was observed below 139 K from both the single-crystal X-ray diffraction and the differential scanning calorimetry analyses. Periodic first-principles calculations within density functional theory show that both P2₁/c superstructure (III) and P2₁ substructure (I) are more stable than P2₁/m structure (II), and that P2₁/c superstructure (III) is more stable that P2₁ substructure (I).

Computing details

For all compounds, data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS2013 (Sheldrick, 2015); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 2012); software used to prepare material for publication: SHELXL2013 (Sheldrick, 2015).

(yzq173) Sodium vanadium dioxide difluoride

Crystal data

NaVO2F2	F(000) = 272
Mr = 143.93	Dx = 3.087 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 6.3846 (18) Å	Cell parameters from 2232 reflections
b = 3.6024 (9) Å	θ = 3.0–28.2°
c = 14.387 (4) Å	µ = 3.21 mm^−1
β = 110.636 (10)°	T = 173 K
V = 309.67 (15) Å^3	Prism, green
Z = 4	0.50 × 0.30 × 0.10 mm

Data collection

Bruker CCD area-detector diffractometer	744 independent reflections
Radiation source: fine-focus sealed tube	726 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.020
1265 images,φ=0, 90, 180 degree, and Δω=0.3 degree, χ= 54.74 degree scans	θmax = 28.6°, θmin = 3.0°
Absorption correction: multi-scan (SMART; Bruker, 2001)	h = −8→8
Tmin = 0.635, Tmax = 0.834	k = −4→4
2232 measured reflections	l = −18→18

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.026	w = 1/[σ^2(Fo^2) + (0.0412P)^2 + 0.4648P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.079	(Δ/σ)max < 0.001
S = 1.08	Δρmax = 0.64 e Å^−3
744 reflections	Δρmin = −0.63 e Å^−3
56 parameters	Extinction correction: SHELXL2013 (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.049 (5)

Special details

Experimental. Data collections were carried out by ω scanning with a step of 0.3° and an exposure time of 6 s per frame. Three groups with total 1800 frames were collected at χ = 54.74°, φ = 0, 90 and 180°, respectively. A total of 2232 observed reflections were collected from 3.03° < θ < 28.56°, of which 744 (R_int = 0.020) were independent, and 726 unique reflections with I > 2σ(I). The crystal structure was solved by direct methods and refined by the full-matrix least-squares method using the SHEXLS2013 and SHELXL2013 software package (Sheldrick, 2015).

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	0.63842 (5)	0.25633 (9)	0.35760 (3)	0.0105 (2)
Na1	0.13432 (13)	0.7154 (2)	0.35395 (6)	0.0120 (3)
F1	0.8790 (2)	0.2135 (3)	0.30904 (10)	0.0115 (3)
F2	0.3595 (2)	0.2138 (3)	0.37051 (11)	0.0135 (3)
O1	0.5941 (2)	0.7251 (3)	0.32098 (12)	0.0107 (3)
O2	0.7874 (3)	0.2637 (4)	0.47197 (13)	0.0196 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
V1	0.0070 (3)	0.0167 (3)	0.0082 (3)	−0.00079 (10)	0.00330 (17)	−0.00107 (10)
Na1	0.0127 (5)	0.0123 (5)	0.0112 (5)	−0.0001 (3)	0.0042 (4)	−0.0001 (3)
F1	0.0082 (6)	0.0152 (6)	0.0119 (6)	0.0001 (4)	0.0047 (5)	0.0001 (4)
F2	0.0107 (6)	0.0143 (6)	0.0182 (6)	−0.0004 (4)	0.0083 (5)	−0.0001 (4)
O1	0.0103 (7)	0.0091 (7)	0.0137 (8)	0.0000 (4)	0.0056 (6)	0.0003 (5)
O2	0.0154 (8)	0.0315 (10)	0.0110 (8)	−0.0016 (6)	0.0037 (6)	−0.0009 (5)

Geometric parameters (Å, º)

V1—O2	1.5843 (18)	Na1—O2^vii	2.376 (2)
V1—O1	1.7618 (14)	Na1—Na1^viii	3.3937 (16)
V1—F2	1.8609 (14)	Na1—Na1^ix	3.3937 (16)
V1—F1	1.9047 (13)	Na1—V1^vi	3.5887 (12)
V1—O1^i	1.9787 (14)	Na1—Na1^i	3.6024 (9)
V1—Na1^ii	3.5887 (12)	Na1—Na1^iii	3.6024 (9)
V1—Na1	3.6024 (12)	F1—Na1^x	2.3163 (16)
Na1—F2^iii	2.2596 (14)	F1—Na1^xi	2.3563 (14)
Na1—F2	2.2687 (14)	F1—Na1^ii	2.3667 (15)
Na1—F1^iv	2.3163 (16)	F2—Na1^i	2.2595 (14)
Na1—F1^v	2.3562 (14)	O1—V1^iii	1.9787 (14)
Na1—F1^vi	2.3667 (15)	O2—Na1^vii	2.376 (2)
O2—V1—O1	105.59 (8)	F2^iii—Na1—V1^vi	153.69 (4)
O2—V1—F2	98.23 (8)	F2—Na1—V1^vi	99.27 (4)
O1—V1—F2	92.88 (6)	F1^iv—Na1—V1^vi	107.19 (4)
O2—V1—F1	96.64 (8)	F1^v—Na1—V1^vi	80.00 (4)
O1—V1—F1	91.91 (6)	F1^vi—Na1—V1^vi	29.03 (3)
F2—V1—F1	162.53 (7)	O2^vii—Na1—V1^vi	81.84 (5)
O2—V1—O1^i	105.66 (7)	Na1^viii—Na1—V1^vi	66.04 (3)
O1—V1—O1^i	148.71 (9)	Na1^ix—Na1—V1^vi	94.76 (4)
F2—V1—O1^i	83.96 (6)	F2^iii—Na1—V1	80.29 (4)
F1—V1—O1^i	83.23 (6)	F2—Na1—V1	26.24 (3)
O2—V1—Na1^ii	78.32 (7)	F1^iv—Na1—V1	74.17 (4)
O1—V1—Na1^ii	66.64 (5)	F1^v—Na1—V1	151.85 (4)
F2—V1—Na1^ii	156.88 (4)	F1^vi—Na1—V1	100.32 (4)
F1—V1—Na1^ii	37.09 (4)	O2^vii—Na1—V1	98.30 (5)
O1^i—V1—Na1^ii	119.08 (5)	Na1^viii—Na1—V1	86.60 (3)
O2—V1—Na1	102.34 (7)	Na1^ix—Na1—V1	115.34 (4)
O1—V1—Na1	60.47 (5)	V1^vi—Na1—V1	125.21 (3)
F2—V1—Na1	32.62 (4)	F2^iii—Na1—Na1^i	142.62 (4)
F1—V1—Na1	149.74 (4)	F2—Na1—Na1^i	37.21 (4)
O1^i—V1—Na1	113.38 (5)	F1^iv—Na1—Na1^i	89.83 (3)
Na1^ii—V1—Na1	125.21 (3)	F1^v—Na1—Na1^i	139.60 (4)
F2^iii—Na1—F2	105.41 (6)	F1^vi—Na1—Na1^i	40.19 (4)
F2^iii—Na1—F1^iv	84.50 (5)	O2^vii—Na1—Na1^i	91.81 (4)
F2—Na1—F1^iv	84.25 (6)	Na1^viii—Na1—Na1^i	57.944 (18)
F2^iii—Na1—F1^v	77.10 (5)	Na1^ix—Na1—Na1^i	122.057 (17)
F2—Na1—F1^v	170.70 (7)	V1^vi—Na1—Na1^i	62.561 (17)
F1^iv—Na1—F1^v	87.11 (5)	V1—Na1—Na1^i	62.673 (17)
F2^iii—Na1—F1^vi	170.83 (7)	F2^iii—Na1—Na1^iii	37.38 (4)
F2—Na1—F1^vi	76.71 (5)	F2—Na1—Na1^iii	142.79 (4)
F1^iv—Na1—F1^vi	86.86 (5)	F1^iv—Na1—Na1^iii	90.17 (3)
F1^v—Na1—F1^vi	99.41 (6)	F1^v—Na1—Na1^iii	40.40 (4)
F2^iii—Na1—O2^vii	88.51 (6)	F1^vi—Na1—Na1^iii	139.81 (4)
F2—Na1—O2^vii	91.40 (6)	O2^vii—Na1—Na1^iii	88.19 (4)
F1^iv—Na1—O2^vii	170.48 (7)	Na1^viii—Na1—Na1^iii	122.056 (18)
F1^v—Na1—O2^vii	97.65 (6)	Na1^ix—Na1—Na1^iii	57.944 (18)
F1^vi—Na1—O2^vii	100.41 (6)	V1^vi—Na1—Na1^iii	117.439 (17)
F2^iii—Na1—Na1^viii	128.30 (6)	V1—Na1—Na1^iii	117.327 (17)
F2—Na1—Na1^viii	76.97 (4)	Na1^i—Na1—Na1^iii	180.0
F1^iv—Na1—Na1^viii	43.89 (4)	V1—F1—Na1^x	128.64 (7)
F1^v—Na1—Na1^viii	94.39 (5)	V1—F1—Na1^xi	122.04 (6)
F1^vi—Na1—Na1^viii	42.98 (4)	Na1^x—F1—Na1^xi	93.15 (5)
O2^vii—Na1—Na1^viii	143.04 (5)	V1—F1—Na1^ii	113.88 (6)
F2^iii—Na1—Na1^ix	77.08 (4)	Na1^x—F1—Na1^ii	92.88 (5)
F2—Na1—Na1^ix	128.32 (6)	Na1^xi—F1—Na1^ii	99.41 (6)
F1^iv—Na1—Na1^ix	44.15 (4)	V1—F2—Na1^i	130.59 (6)
F1^v—Na1—Na1^ix	42.96 (4)	V1—F2—Na1	121.15 (6)
F1^vi—Na1—Na1^ix	94.55 (5)	Na1^i—F2—Na1	105.41 (6)
O2^vii—Na1—Na1^ix	139.95 (5)	V1—O1—V1^iii	148.71 (9)
Na1^viii—Na1—Na1^ix	64.11 (3)	V1—O2—Na1^vii	157.15 (11)

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

(yzq295) Sodium vanadium dioxide difluoride

Crystal data

NaVO2F2	F(000) = 272
Mr = 143.93	Dx = 3.051 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 6.400 (5) Å	Cell parameters from 1882 reflections
b = 3.614 (2) Å	θ = 3.0–28.6°
c = 14.453 (12) Å	µ = 3.17 mm^−1
β = 110.369 (10)°	T = 295 K
V = 313.4 (6) Å^3	Prism, green
Z = 4	0.40 × 0.20 × 0.10 mm

Data collection

Bruker CCD area-detector diffractometer	728 independent reflections
Radiation source: fine-focus sealed tube	685 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.025
1265 images,φ=0, 90, 180 degree, and Δω=0.3 degree, χ= 54.74 degree scans	θmax = 28.6°, θmin = 3.4°
Absorption correction: multi-scan (SMART; Bruker, 2001)	h = −8→8
Tmin = 0.556, Tmax = 0.834	k = −4→4
1711 measured reflections	l = −13→19

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.051	w = 1/[σ^2(Fo^2) + (0.0998P)^2 + 0.8843P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.157	(Δ/σ)max = 0.001
S = 1.04	Δρmax = 1.17 e Å^−3
728 reflections	Δρmin = −0.92 e Å^−3
56 parameters	Extinction correction: SHELXL2013 (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.067 (11)

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	0.63884 (10)	0.25482 (13)	0.35808 (5)	0.0156 (4)
Na1	0.1347 (2)	0.7287 (3)	0.35399 (12)	0.0175 (5)
F1	0.8782 (4)	0.2276 (5)	0.30933 (19)	0.0159 (6)
F2	0.3596 (4)	0.2276 (5)	0.3704 (2)	0.0193 (6)
O1	0.5939 (4)	0.7349 (5)	0.3214 (2)	0.0148 (6)
O2	0.7861 (6)	0.2599 (7)	0.4717 (2)	0.0300 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
V1	0.0097 (5)	0.0248 (6)	0.0137 (6)	−0.00061 (16)	0.0060 (3)	−0.00079 (16)
Na1	0.0191 (10)	0.0159 (9)	0.0181 (10)	−0.0004 (4)	0.0073 (8)	−0.0006 (4)
F1	0.0110 (11)	0.0203 (11)	0.0191 (12)	0.0005 (6)	0.0086 (9)	−0.0005 (6)
F2	0.0148 (11)	0.0185 (11)	0.0299 (13)	0.0000 (6)	0.0145 (10)	−0.0002 (7)
O1	0.0153 (13)	0.0097 (12)	0.0216 (15)	0.0005 (7)	0.0092 (12)	0.0006 (7)
O2	0.0222 (16)	0.050 (2)	0.0161 (16)	−0.0025 (10)	0.0046 (13)	−0.0020 (9)

Geometric parameters (Å, º)

V1—O2	1.584 (4)	Na1—O2^vii	2.390 (5)
V1—O1	1.808 (3)	Na1—Na1^viii	3.416 (4)
V1—F2	1.859 (3)	Na1—Na1^ix	3.416 (4)
V1—F1	1.899 (3)	Na1—Na1^iii	3.614 (4)
V1—O1^i	1.946 (3)	Na1—Na1^i	3.614 (4)
V1—Na1^ii	3.625 (3)	Na1—V1^vi	3.625 (3)
V1—Na1	3.635 (4)	F1—Na1^x	2.333 (4)
Na1—F2^iii	2.267 (3)	F1—Na1^xi	2.372 (3)
Na1—F2	2.274 (3)	F1—Na1^ii	2.378 (3)
Na1—F1^iv	2.333 (4)	F2—Na1^i	2.267 (3)
Na1—F1^v	2.372 (3)	O1—V1^iii	1.946 (3)
Na1—F1^vi	2.378 (3)	O2—Na1^vii	2.390 (5)
O2—V1—O1	105.63 (13)	F2^iii—Na1—Na1^iii	37.33 (7)
O2—V1—F2	98.40 (17)	F2—Na1—Na1^iii	142.79 (7)
O1—V1—F2	91.08 (10)	F1^iv—Na1—Na1^iii	90.10 (5)
O2—V1—F1	96.89 (18)	F1^v—Na1—Na1^iii	40.52 (7)
O1—V1—F1	90.42 (10)	F1^vi—Na1—Na1^iii	139.61 (7)
F2—V1—F1	163.63 (13)	O2^vii—Na1—Na1^iii	89.02 (6)
O2—V1—O1^i	105.78 (12)	Na1^viii—Na1—Na1^iii	121.94 (5)
O1—V1—O1^i	148.58 (18)	Na1^ix—Na1—Na1^iii	58.06 (5)
F2—V1—O1^i	85.37 (10)	F2^iii—Na1—Na1^i	142.67 (7)
F1—V1—O1^i	84.87 (10)	F2—Na1—Na1^i	37.21 (7)
O2—V1—Na1^ii	78.66 (13)	F1^iv—Na1—Na1^i	89.90 (5)
O1—V1—Na1^ii	65.95 (10)	F1^v—Na1—Na1^i	139.48 (7)
F2—V1—Na1^ii	154.53 (7)	F1^vi—Na1—Na1^i	40.39 (7)
F1—V1—Na1^ii	36.32 (7)	O2^vii—Na1—Na1^i	90.98 (6)
O1^i—V1—Na1^ii	119.92 (9)	Na1^viii—Na1—Na1^i	58.06 (5)
O2—V1—Na1	102.44 (13)	Na1^ix—Na1—Na1^i	121.94 (5)
O1—V1—Na1	59.57 (9)	Na1^iii—Na1—Na1^i	180.0
F2—V1—Na1	31.70 (7)	F2^iii—Na1—V1^vi	154.37 (8)
F1—V1—Na1	147.64 (8)	F2—Na1—V1^vi	98.51 (10)
O1^i—V1—Na1	113.85 (9)	F1^iv—Na1—V1^vi	107.02 (7)
Na1^ii—V1—Na1	123.66 (8)	F1^v—Na1—V1^vi	80.60 (10)
F2^iii—Na1—F2	105.46 (14)	F1^vi—Na1—V1^vi	28.22 (6)
F2^iii—Na1—F1^iv	84.53 (10)	O2^vii—Na1—V1^vi	81.76 (9)
F2—Na1—F1^iv	84.38 (10)	Na1^viii—Na1—V1^vi	65.65 (6)
F2^iii—Na1—F1^v	77.18 (12)	Na1^ix—Na1—V1^vi	95.03 (8)
F2—Na1—F1^v	170.72 (13)	Na1^iii—Na1—V1^vi	118.20 (4)
F1^iv—Na1—F1^v	87.05 (9)	Na1^i—Na1—V1^vi	61.80 (4)
F2^iii—Na1—F1^vi	170.81 (13)	F2^iii—Na1—V1	81.10 (10)
F2—Na1—F1^vi	76.93 (12)	F2—Na1—V1	25.44 (6)
F1^iv—Na1—F1^vi	86.90 (9)	F1^iv—Na1—V1	74.59 (6)
F1^v—Na1—F1^vi	99.10 (13)	F1^v—Na1—V1	152.75 (7)
F2^iii—Na1—O2^vii	88.98 (11)	F1^vi—Na1—V1	99.82 (10)
F2—Na1—O2^vii	90.55 (11)	O2^vii—Na1—V1	97.43 (9)
F1^iv—Na1—O2^vii	170.39 (13)	Na1^viii—Na1—V1	86.47 (7)
F1^v—Na1—O2^vii	98.43 (11)	Na1^ix—Na1—V1	115.91 (8)
F1^vi—Na1—O2^vii	99.92 (11)	Na1^iii—Na1—V1	118.11 (4)
F2^iii—Na1—Na1^viii	128.33 (11)	Na1^i—Na1—V1	61.89 (4)
F2—Na1—Na1^viii	77.15 (9)	V1^vi—Na1—V1	123.66 (8)
F1^iv—Na1—Na1^viii	43.89 (8)	V1—F1—Na1^x	128.78 (13)
F1^v—Na1—Na1^viii	94.19 (11)	V1—F1—Na1^xi	120.66 (12)
F1^vi—Na1—Na1^viii	43.01 (7)	Na1^x—F1—Na1^xi	93.10 (9)
O2^vii—Na1—Na1^viii	142.50 (9)	V1—F1—Na1^ii	115.46 (11)
F2^iii—Na1—Na1^ix	77.23 (9)	Na1^x—F1—Na1^ii	92.94 (9)
F2—Na1—Na1^ix	128.34 (11)	Na1^xi—F1—Na1^ii	99.10 (13)
F1^iv—Na1—Na1^ix	44.05 (8)	V1—F2—Na1^i	128.95 (11)
F1^v—Na1—Na1^ix	43.00 (7)	V1—F2—Na1	122.86 (11)
F1^vi—Na1—Na1^ix	94.28 (10)	Na1^i—F2—Na1	105.46 (14)
O2^vii—Na1—Na1^ix	140.83 (9)	V1—O1—V1^iii	148.58 (18)
Na1^viii—Na1—Na1^ix	63.88 (9)	V1—O2—Na1^vii	157.6 (2)

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

(yzq495) Sodium vanadium dioxide difluoride

Crystal data

NaVO2F2	Z = 2
Mr = 143.93	F(000) = 136
Monoclinic, P21/m	Dx = 3.069 Mg m^−3
a = 6.369 (5) Å	Mo Kα radiation, λ = 0.71073 Å
b = 3.625 (2) Å	µ = 3.19 mm^−1
c = 7.196 (6) Å	T = 295 K
β = 110.37 (4)°	Prism, green
V = 155.7 (4) Å^3	0.45 × 0.11 × 0.11 mm

Data collection

Bruker CCD area-detector diffractometer	422 independent reflections
Radiation source: fine-focus sealed tube	410 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.019
1265 images,φ=0, 90, 180 degree, and Δω=0.3 degree, χ= 54.74 degree scans	θmax = 28.4°, θmin = 3.0°
Absorption correction: multi-scan (SMART; Bruker, 2001)	h = −5→8
Tmin = 0.543, Tmax = 0.736	k = −4→4
960 measured reflections	l = −9→9

Refinement

Refinement on F^2	37 parameters
Least-squares matrix: full	0 restraints
R[F^2 > 2σ(F^2)] = 0.028	w = 1/[σ^2(Fo^2) + (0.0508P)^2 + 0.0945P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.078	(Δ/σ)max < 0.001
S = 1.09	Δρmax = 0.47 e Å^−3
422 reflections	Δρmin = −0.46 e Å^−3

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	0.36125 (7)	0.2500	0.28387 (7)	0.0185 (2)
Na1	0.13500 (18)	0.2500	0.70839 (17)	0.0196 (3)
F1	0.1213 (3)	0.2500	0.3815 (3)	0.0178 (4)
F2	0.6398 (3)	0.2500	0.2589 (3)	0.0215 (4)
O1	0.5938 (3)	0.2500	0.6430 (3)	0.0159 (4)
O2	0.2142 (4)	0.2500	0.0565 (3)	0.0347 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
V1	0.0093 (3)	0.0328 (4)	0.0150 (3)	0.000	0.0064 (2)	0.000
Na1	0.0182 (7)	0.0222 (7)	0.0198 (7)	0.000	0.0084 (5)	0.000
F1	0.0113 (8)	0.0244 (9)	0.0203 (8)	0.000	0.0088 (7)	0.000
F2	0.0136 (8)	0.0253 (9)	0.0306 (9)	0.000	0.0142 (7)	0.000
O1	0.0156 (9)	0.0133 (9)	0.0215 (10)	0.000	0.0098 (8)	0.000
O2	0.0213 (11)	0.0633 (18)	0.0186 (12)	0.000	0.0057 (10)	0.000

Geometric parameters (Å, º)

V1—O2	1.577 (3)	Na1—O2^v	2.377 (4)
V1—F2	1.844 (3)	Na1—Na1^iii	3.413 (4)
V1—O1^i	1.881 (2)	Na1—Na1^iv	3.413 (4)
V1—O1^ii	1.881 (2)	Na1—Na1^vi	3.625 (5)
V1—F1	1.891 (3)	Na1—Na1^vii	3.625 (5)
V1—Na1^iii	3.661 (4)	Na1—V1^iii	3.661 (4)
V1—Na1^iv	3.661 (4)	Na1—V1^iv	3.661 (4)
V1—Na1^i	3.668 (4)	F1—Na1^iii	2.373 (3)
V1—Na1^ii	3.668 (4)	F1—Na1^iv	2.373 (3)
Na1—F2^i	2.272 (3)	F2—Na1^i	2.272 (3)
Na1—F2^ii	2.272 (3)	F2—Na1^ii	2.272 (3)
Na1—F1	2.323 (4)	O1—V1^i	1.881 (2)
Na1—F1^iii	2.373 (3)	O1—V1^ii	1.881 (2)
Na1—F1^iv	2.373 (3)	O2—Na1^viii	2.377 (4)
O2—V1—F2	98.23 (13)	F2^i—Na1—Na1^iv	76.95 (9)
O2—V1—O1^i	105.54 (7)	F2^ii—Na1—Na1^iv	128.43 (9)
F2—V1—O1^i	88.25 (6)	F1—Na1—Na1^iv	43.98 (7)
O2—V1—O1^ii	105.54 (7)	F1^iii—Na1—Na1^iv	94.45 (10)
F2—V1—O1^ii	88.25 (6)	F1^iv—Na1—Na1^iv	42.82 (6)
O1^i—V1—O1^ii	148.91 (13)	O2^v—Na1—Na1^iv	141.56 (7)
O2—V1—F1	96.91 (14)	Na1^iii—Na1—Na1^iv	64.16 (10)
F2—V1—F1	164.86 (9)	F2^i—Na1—Na1^vi	142.91 (6)
O1^i—V1—F1	87.71 (6)	F2^ii—Na1—Na1^vi	37.09 (6)
O1^ii—V1—F1	87.71 (6)	F1—Na1—Na1^vi	90.0
O2—V1—Na1^iii	79.14 (10)	F1^iii—Na1—Na1^vi	40.21 (6)
F2—V1—Na1^iii	150.04 (5)	F1^iv—Na1—Na1^vi	139.79 (6)
O1^i—V1—Na1^iii	121.39 (7)	O2^v—Na1—Na1^vi	90.0
O1^ii—V1—Na1^iii	64.33 (8)	Na1^iii—Na1—Na1^vi	57.92 (5)
F1—V1—Na1^iii	34.99 (5)	Na1^iv—Na1—Na1^vi	122.08 (5)
O2—V1—Na1^iv	79.14 (10)	F2^i—Na1—Na1^vii	37.09 (6)
F2—V1—Na1^iv	150.04 (5)	F2^ii—Na1—Na1^vii	142.91 (6)
O1^i—V1—Na1^iv	64.33 (8)	F1—Na1—Na1^vii	90.0
O1^ii—V1—Na1^iv	121.39 (7)	F1^iii—Na1—Na1^vii	139.79 (6)
F1—V1—Na1^iv	34.99 (5)	F1^iv—Na1—Na1^vii	40.21 (6)
Na1^iii—V1—Na1^iv	59.36 (9)	O2^v—Na1—Na1^vii	90.0
O2—V1—Na1^i	102.49 (10)	Na1^iii—Na1—Na1^vii	122.08 (5)
F2—V1—Na1^i	30.19 (5)	Na1^iv—Na1—Na1^vii	57.92 (5)
O1^i—V1—Na1^i	58.17 (7)	Na1^vi—Na1—Na1^vii	180.0
O1^ii—V1—Na1^i	115.13 (8)	F2^i—Na1—V1^iii	155.59 (5)
F1—V1—Na1^i	144.09 (6)	F2^ii—Na1—V1^iii	96.94 (10)
Na1^iii—V1—Na1^i	178.37 (4)	F1—Na1—V1^iii	106.68 (6)
Na1^iv—V1—Na1^i	120.69 (9)	F1^iii—Na1—V1^iii	27.19 (4)
O2—V1—Na1^ii	102.49 (10)	F1^iv—Na1—V1^iii	82.34 (11)
F2—V1—Na1^ii	30.19 (5)	O2^v—Na1—V1^iii	81.46 (7)
O1^i—V1—Na1^ii	115.13 (8)	Na1^iii—Na1—V1^iii	64.96 (7)
O1^ii—V1—Na1^ii	58.17 (7)	Na1^iv—Na1—V1^iii	95.90 (8)
F1—V1—Na1^ii	144.09 (6)	Na1^vi—Na1—V1^iii	60.32 (5)
Na1^iii—V1—Na1^ii	120.69 (9)	Na1^vii—Na1—V1^iii	119.68 (5)
Na1^iv—V1—Na1^ii	178.37 (4)	F2^i—Na1—V1^iv	96.94 (10)
Na1^i—V1—Na1^ii	59.22 (9)	F2^ii—Na1—V1^iv	155.59 (5)
F2^i—Na1—F2^ii	105.81 (13)	F1—Na1—V1^iv	106.68 (6)
F2^i—Na1—F1	84.53 (7)	F1^iii—Na1—V1^iv	82.34 (11)
F2^ii—Na1—F1	84.53 (7)	F1^iv—Na1—V1^iv	27.19 (4)
F2^i—Na1—F1^iii	170.71 (9)	O2^v—Na1—V1^iv	81.46 (7)
F2^ii—Na1—F1^iii	76.62 (11)	Na1^iii—Na1—V1^iv	95.90 (8)
F1—Na1—F1^iii	86.80 (7)	Na1^iv—Na1—V1^iv	64.96 (7)
F2^i—Na1—F1^iv	76.62 (11)	Na1^vi—Na1—V1^iv	119.68 (5)
F2^ii—Na1—F1^iv	170.71 (9)	Na1^vii—Na1—V1^iv	60.32 (5)
F1—Na1—F1^iv	86.80 (7)	V1^iii—Na1—V1^iv	59.36 (9)
F1^iii—Na1—F1^iv	99.57 (13)	V1—F1—Na1	128.74 (10)
F2^i—Na1—O2^v	89.78 (7)	V1—F1—Na1^iii	117.83 (8)
F2^ii—Na1—O2^v	89.78 (7)	Na1—F1—Na1^iii	93.20 (7)
F1—Na1—O2^v	170.55 (9)	V1—F1—Na1^iv	117.83 (8)
F1^iii—Na1—O2^v	99.25 (7)	Na1—F1—Na1^iv	93.20 (7)
F1^iv—Na1—O2^v	99.25 (7)	Na1^iii—F1—Na1^iv	99.57 (13)
F2^i—Na1—Na1^iii	128.43 (9)	V1—F2—Na1^i	125.72 (7)
F2^ii—Na1—Na1^iii	76.95 (9)	V1—F2—Na1^ii	125.72 (7)
F1—Na1—Na1^iii	43.98 (7)	Na1^i—F2—Na1^ii	105.82 (13)
F1^iii—Na1—Na1^iii	42.82 (6)	V1^i—O1—V1^ii	148.91 (13)
F1^iv—Na1—Na1^iii	94.45 (10)	V1—O2—Na1^viii	157.63 (15)
O2^v—Na1—Na1^iii	141.56 (7)

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