A new chain structure: catena-poly[4,4′-(ethane-1,2-diyl)dipyridinium bis­[[aqua­difluorido­oxido­vanadate]-μ-fluorido]]

The title compound, {(C₁₂H₁₂N₂)[V₂F₆O₂(H₂O)₂]}_n, features a novel extended-chain moiety, [VOF₂F_2/2(H₂O)]_n, comprising trans vertex-connected VOF₄(H₂O) octa­hedra. The octa­hedra themselves show the characteristic distortion due to the off-centring of the V⁴⁺ ion, such that a short terminal V=O bond and an elongated trans V—OH₂ bond are present. Hydrogen bonding from the water mol­ecules to terminal F atoms in adjacent chains generates associated chain dimers, which are loosely linked into sheets via additional hydrogen bonding involving the organic moieties. Structural relationships with previously described vanadium oxyfluoride species are briefly discussed.

S1. Comment

The title compound, (I), was isolated during a more general survey of the solvothermal chemistry of vanadium oxyfluorides incorporating organic amines (Aldous et al., 2007a,b).

The building unit of (I) (Fig. 1) exhibits a single V site in a distorted octahedral environment and a diprotonated 4,4'-ethane-1,2-diyldipyridinium ligand (bpeH₂) located on an inversion centre. The short V═O and longer trans V—OH₂ bond lengths are comparable with those seen in previous examples of the polar VOF₄(H₂O) moiety (Stephens et al., 1995; Aldous et al., 2007a). The octahedral units are linked through trans fluoride ligands, F1, to produce a novel infinite chain motif.

Bond-valence sum analysis (Brese & O'Keeffe, 1991) (Table 2) confirms the assignment of the V centre as V⁴⁺, and reveals underbonding at the terminal F sites F2 and F3. These sites therefore accept hydrogen bonds, F3 from the water molecules in neighbouring chains and F2 from the organic group (Table 1). This results in pairs of associated inorganic chains (Fig. 2a), which are weakly associated into layers via the bpeH₂ ligands (Fig. 3).

Apart from the novelty of the chain unit itself, the most significant feature of this structure lies in the relationship of the chain architecture to the `ladder-like' (VOF<sub>3</sub>) chains previously observed in the same synthetic system. The ladder units in [C<sub>12</sub>H<sub>12</sub>N<sub>2</sub>](VOF<sub>3</sub>)<sub>2</sub> (Aldous, Goff et al., 2007) are shown in Fig. 2(b). This compound was prepared from an identical reaction mixture under identical reaction conditions to those used for (I), except that the temperature was raised from 333 to 373 K for the ladder. One can therefore speculate that, in the preparation of the ladder phase, hydrogen-bonded dimerized chains of the type observed in (I) (Fig. 2a) are formed initially and then condense into the ladder chains at elevated temperatures, via the loss of the water ligands and fusion of adjacent chains through bonding of terminal F atoms, F3 in the case of (I), to the adjacent V centre. We have also shown recently (Himeur et al., 2010) that a similar condensation mechanism could occur to produce extended sheet architectures of composition (VOF<sub>2.5</sub>) from (VOF<sub>3</sub>) ladders by using a different solvent, in fact an ionic liquid. The isolation of (I) therefore adds a `missing piece of the jigsaw' in understanding the formation of extended vanadium oxyfluorides from oligomeric building blocks in solvothermal systems.

We also note that further examples of a `VOF<sub>3</sub>(H<sub>2</sub>O)' compositional group occur in the Cambridge Structural Database (CSD, Version?; Allen, 2002, but these apparent compositional similarities to (I) belie any exact structural similarity, as the previous examples are based upon edge-sharing dimeric units, `V₂O₂F₆(H₂O)₂', with either axial (Bukovec et al., 1981; Demsar & Bukovec, 1984) or equatorial (Aldous et al., 2007b) H₂O groups, rather than the present infinite chain motif.

S2. Experimental

Vanadium pentoxide (0.1819 g), water (5 ml) and a 40% solution of HF (0.5 ml) were heated in a polypropylene bottle at 373 K for 1 h. To the contents of the bottle, ethylene glycol (5 ml) and 4,4'-ethane-1,2-diyldipyridine (0.5338 g) were added. The resulting mixture was heated at 333 K for 2 d and then allowed to cool naturally to ambient temperature. The final product was filtered off, washed in water and allowed to dry overnight at 333 K. Crystals of (I) are blue platelets of typical dimension 0.2 × 0.1 × 0.01 mm. Phase purity was confirmed by powder X-ray diffraction of the bulk product and by elemental analysis; found (%): C 31.32, H 3.20, N 5.93; calculated for C₁₂H₁₆F₆N₂O₄V₂ (%): C 30.79, H 3.44, N 5.98. Magnetic susceptibility measuremements revealed (I) to be paramagnetic down to 2 K.

S3. Refinement

H atoms attached to C and N atoms were placed in geometrically idealized positions and refined using a riding model, with C—H = 0.95 Å and N—H = 0.88 Å, and with U_iso(H) = 1.2U_eq(C,N). [Please check added text] Water H atoms were located in a difference Fourier map and then refined isotropically with an O—H bond-length restraint of 0.85 (2) Å.

Computing details

Data collection: CrystalClear (Rigaku, 2004); cell refinement: CrystalClear (Rigaku, 2004); data reduction: CrystalClear (Rigaku, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2009); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. The building unit of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. [Symmetry codes: (i) -1 + x, y, z; (ii) -2 - x,-y, 2 - z.]
	Fig. 2. (a) Pairs of hydrogen-bonded (fine lines) chains of (I), extending along [100]. (b) Ladder-like chains of stoichiometry (VOF3), observed previously in [bpeH2](VOF3)2 (Aldous, Goff et al., 2007). By comparison with Fig. 2(a), the condensation of the hydrogen-bonded chains in (I) to ladders in this compound can be visualized.
	Fig. 3. The crystal packing of (I) along [100], showing the chain dimers and further hydrogen bonding (fine lines) from the (bpeH2) moieties.

catena-poly[4,4'-(ethane-1,2-diyl)dipyridinium bis[[aquadifluoridooxidovanadate]-µ-fluorido]]

Crystal data

(C12H12N2)[V2F6O2(H2O)2]	Z = 1
Mr = 468.15	F(000) = 234
Triclinic, P1	Dx = 1.992 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71075 Å
a = 3.7797 (17) Å	Cell parameters from 1529 reflections
b = 10.362 (3) Å	θ = 3.6–29.0°
c = 11.297 (3) Å	µ = 1.29 mm^−1
α = 62.92 (2)°	T = 93 K
β = 82.30 (3)°	Platelet, blue
γ = 87.60 (4)°	0.12 × 0.10 × 0.02 mm
V = 390.3 (2) Å^3

Data collection

Rigaku Model? CCD area-detector diffractometer	1385 independent reflections
Radiation source: Rotating anode	1215 reflections with I > 2σ(I)
Confocal optics monochromator	Rint = 0.024
dtprofit.ref scans	θmax = 25.3°, θmin = 3.6°
Absorption correction: multi-scan (SADABS; Bruker, 1999)	h = −4→4
Tmin = 0.864, Tmax = 1.000	k = −12→12
2526 measured reflections	l = −13→11

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)] = 0.033	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.080	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0393P)^2 + 0.0941P] where P = (Fo^2 + 2Fc^2)/3
1385 reflections	(Δ/σ)max < 0.001
126 parameters	Δρmax = 0.36 e Å^−3
2 restraints	Δρmin = −0.34 e Å^−3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 (Ų)

	x	y	z	Uiso*/Ueq
V1	0.18095 (12)	0.34036 (5)	0.24779 (4)	0.01371 (18)
F1	0.6660 (4)	0.37177 (17)	0.22565 (15)	0.0240 (4)
F3	0.2296 (4)	0.30350 (15)	0.09384 (13)	0.0125 (3)
F2	0.0845 (4)	0.42236 (15)	0.36991 (14)	0.0136 (3)
O2	0.2027 (5)	0.5735 (2)	0.09098 (18)	0.0123 (4)
O1	0.1425 (5)	0.17421 (18)	0.36020 (17)	0.0144 (4)
H11	0.042 (7)	0.604 (4)	0.042 (3)	0.040 (10)*
H12	0.403 (6)	0.604 (4)	0.048 (3)	0.051 (12)*
N1	−0.3623 (6)	0.2562 (2)	0.5793 (2)	0.0116 (5)
H1	−0.2303	0.3112	0.5033	0.014*
C1	−0.4846 (7)	0.3127 (3)	0.6624 (2)	0.0142 (6)
H1A	−0.4308	0.4110	0.6382	0.017*
C2	−0.4350 (7)	0.1187 (3)	0.6083 (2)	0.0129 (6)
H2	−0.3487	0.0824	0.5466	0.015*
C3	−0.6875 (7)	0.2287 (3)	0.7826 (3)	0.0150 (6)
H3	−0.7765	0.2692	0.8409	0.018*
C4	−0.6344 (7)	0.0306 (3)	0.7276 (3)	0.0127 (6)
H4	−0.6861	−0.0669	0.7483	0.015*
C5	−0.7623 (7)	0.0839 (3)	0.8189 (2)	0.0116 (5)
C6	−0.9611 (7)	−0.0148 (3)	0.9481 (2)	0.0128 (6)
H6	−1.0397	−0.1058	0.9586	0.015*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
V1	0.0215 (3)	0.0103 (3)	0.0084 (3)	0.0009 (2)	0.00072 (19)	−0.0042 (2)
F1	0.0202 (9)	0.0289 (10)	0.0259 (9)	0.0003 (7)	−0.0036 (7)	−0.0148 (8)
F3	0.0123 (8)	0.0139 (8)	0.0120 (7)	−0.0017 (6)	−0.0001 (6)	−0.0069 (7)
F2	0.0163 (8)	0.0140 (8)	0.0120 (7)	−0.0052 (6)	0.0032 (6)	−0.0080 (7)
O2	0.0095 (10)	0.0130 (10)	0.0118 (9)	−0.0008 (8)	−0.0006 (8)	−0.0036 (8)
O1	0.0167 (10)	0.0113 (10)	0.0126 (9)	−0.0003 (8)	0.0017 (8)	−0.0041 (8)
N1	0.0116 (11)	0.0114 (11)	0.0063 (10)	−0.0009 (9)	0.0009 (9)	0.0001 (9)
C1	0.0168 (14)	0.0117 (14)	0.0141 (13)	−0.0014 (11)	−0.0011 (11)	−0.0059 (12)
C2	0.0150 (14)	0.0140 (14)	0.0109 (13)	0.0014 (11)	−0.0030 (11)	−0.0064 (12)
C3	0.0174 (14)	0.0160 (14)	0.0134 (13)	−0.0015 (12)	0.0015 (11)	−0.0090 (12)
C4	0.0143 (13)	0.0096 (13)	0.0130 (13)	−0.0015 (11)	−0.0006 (11)	−0.0043 (11)
C5	0.0084 (12)	0.0124 (13)	0.0123 (13)	−0.0014 (10)	−0.0019 (10)	−0.0040 (11)
C6	0.0109 (13)	0.0101 (13)	0.0144 (13)	−0.0027 (11)	0.0003 (11)	−0.0034 (11)

Geometric parameters (Å, º)

V1—O1	1.6058 (19)	C1—C3	1.375 (4)
V1—F1	1.8393 (18)	C1—H1A	0.9500
V1—F2	1.9144 (14)	C2—C4	1.372 (4)
V1—F3	1.9281 (14)	C2—H2	0.9500
V1—F1^i	1.9899 (18)	C3—C5	1.395 (4)
V1—O2	2.250 (2)	C3—H3	0.9500
F1—V1^ii	1.9899 (18)	C4—C5	1.402 (3)
O2—H11	0.830 (18)	C4—H4	0.9500
O2—H12	0.833 (19)	C5—C6	1.467 (3)
N1—C2	1.341 (3)	C6—C6^iii	1.336 (5)
N1—C1	1.341 (3)	C6—H6	0.9500
N1—H1	0.8800
O1—V1—F1	101.28 (10)	C2—N1—H1	119.0
O1—V1—F2	95.89 (8)	C1—N1—H1	119.0
F1—V1—F2	93.54 (7)	N1—C1—C3	120.2 (2)
O1—V1—F3	97.08 (8)	N1—C1—H1A	119.9
F1—V1—F3	90.43 (7)	C3—C1—H1A	119.9
F2—V1—F3	165.42 (7)	N1—C2—C4	119.7 (2)
O1—V1—F1^i	97.17 (9)	N1—C2—H2	120.1
F1—V1—F1^i	161.54 (10)	C4—C2—H2	120.1
F2—V1—F1^i	85.08 (7)	C1—C3—C5	119.8 (2)
F3—V1—F1^i	86.71 (7)	C1—C3—H3	120.1
O1—V1—O2	176.92 (8)	C5—C3—H3	120.1
F1—V1—O2	81.78 (9)	C2—C4—C5	120.3 (2)
F2—V1—O2	83.61 (7)	C2—C4—H4	119.9
F3—V1—O2	83.08 (7)	C5—C4—H4	119.9
F1^i—V1—O2	79.77 (8)	C3—C5—C4	117.9 (2)
V1—F1—V1^ii	161.54 (10)	C3—C5—C6	123.2 (2)
V1—O2—H11	119 (2)	C4—C5—C6	119.0 (2)
V1—O2—H12	115 (3)	C6^iii—C6—C5	124.3 (3)
H11—O2—H12	111 (3)	C6^iii—C6—H6	117.9
C2—N1—C1	122.1 (2)	C5—C6—H6	117.9

Symmetry codes: (i) x−1, y, z; (ii) x+1, y, z; (iii) −x−2, −y, −z+2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···F2	0.88	1.75	2.622 (3)	170
O2—H11···F3^iv	0.83 (2)	1.82 (2)	2.640 (3)	167 (4)
O2—H12···F3^v	0.83 (2)	1.88 (2)	2.682 (3)	162 (4)

Symmetry codes: (iv) −x, −y+1, −z; (v) −x+1, −y+1, −z.