Penta­aqua­oxovanadium(IV) bis(trifluoro­methane­sulfonate)

The structure of the penta­aqua­oxo­vanadium(IV) ion in a salt with singly charged counter-ions is presented. In [VO(H₂O)₅](CF₃SO₃)₂, the six-coordinate V atom is coordinated to the oxo group with a short bond [1.577 (2) Å]. The equatorial V-O bond lengths are 2.0262 (18) and 2.0277 (17) Å. The aqua ligand trans to the oxo group is subject to its trans influence, which leads to a somewhat longer V-O bond [2.175 (2) Å]. In the structure, the cation and both anions are situated on crystallographic mirror planes. The cation and anions engage in a number of relatively long hydrogen bonds [2.725 (2)-2.834 (2) Å].

S1. Comment

The archetypical mono-oxo complex of transition metals is the vanadyl ion (VO²⁺; Jørgensen, 1957; Ballhausen & Gray, 1962). Although numerous structural characterizations of anionic and neutral complexes containing the vanadyl group have been undertaken (Nugent & Mayer, 1988), there exist very few structurally characterized examples of cationic vanadyl complexes (Seifert & Uebach, 1981). Prompted by its simple electronic structure and by its use as a spin-probe in bioinorganic and materials chemistry, several studies have dealt with the structure of the vanadyl aqua ion in solution (Smith et al., 2002; Mustafi et al., 1999; Mustafi & Makinen, 1988; van Willigen et al., 1982). The solution structure has been determined by combined application of electron paramagnetic resonance (EPR), high-freqency (high-field) EPR, electron nuclear double resonance and UV–vis spectroscopies. In the solid state, the vanadyl aqua ions have been characterized in various hydrated sulfate salts; however the majority of these are either oligomeric or contain coordinated sulfate (Palma-Vittorelli et al., 1956). The parent aqua ion, [VO(H₂O)₅]²⁺ is only present in V(O)(SO₄)·6H₂O and one of the modifications of V(O)(SO₄)·5H₂O (Hawthorne et al., 2001; Tachez & Théobald, 1980). Recently, Tézé et al. (2000) isolated, for the first time, a structure without sulfate counter-ions, containing the pentaaquaoxovanadium(IV) complex, namely [Na(H₂O)₂][VO(H₂O)₅][SiW₁₂O₄₀]·4H₂O. Refinement of this farily complicated structure yielded a structure with 0.01–0.02 Å standard deviations on the V—O bond lengths. We have found that metathesis of vanadylsulfate with bariumtriflate to yield a salt of the weakly coordinating trifluoromethanesulfonate ion, [V(O)(H₂O)₅](CF₃SO₃)₂, (I), is possible. This salt, although very hygroscopic, can be crystallized from aqueous solution. The cation in (I), which is depicted in Fig. 1, is six-coordinate with a vanadium–oxo bond length of 1.577 (2) Å, which is slightly, but significantly, shorter than the average of structurally characterized vanadyl(IV) systems. The equatorial water ligands are coordinated at normal distances [2.0262 (18) and 2.0277 (17) Å], while the trans influence [V—O^trans = 2.175 (2) Å] is less pronounced than for most other sixcoordinate vanadium(IV) systems. In the present structure all of the H atoms were located from a difference density map, which allows for comments on the coordination mode of the aqua ligands. These are found to have neither purely tetrahedral nor purely planar coordination, but the trans water approaches the planar coordination mode with its plane bisecting the bond directions from vanadium to the equatorial ligands. This conformation is the same as that found in the sulfates (Tachez & Théobald, 1980). The V atom is raised out of the plane of the four equatorial oxygen donors towards the terminal oxo group by 0.2880 (12) Å, which is an unexceptional degree of pyramidalization for V^IV, but significantly larger than what is usually found for cationic complexes of Mo^IV (0.11 Å; Bendix & Bøgevig, 1998a) or W^IV (0.10–0.17 Å; Bendix & Bøgevig, 1998b). The unit O^oxo—V—O^trans is almost linear with a bond angle of 174.23 (12)°, indicating only weak interaction of the trans water ligand with the counter-ions (see below).

As expected from the composition, the structure is held together by several hydrogen bonds, although these are not very short. The symmetry-independent equatorial water molecules each engage in two roughly linear hydrogen bonds to the O atoms of neighboring trifluoromethanesulfonate anions. The water trans to the oxo group is expected to be less acidic and, in line with this, it only engages in a single hydrogen bond, which is longer than the others. The packing including these hydrogen bonds is shown in Fig. 2 and the hydrogen-bond lengths are tabulated in Table 2. The structure of the trifluoromethanesulfonate counter-anions are unexceptional and their lack of coordination expected.

The structure determined here agrees well with the earlier literature. Specifically, we find all the V—O bond distances except that to the trans-situated water ligand identical within the experimental errors to those determined by Tézé et al. (2000).

Related literature

For related literature, see: Ballhausen & Gray (1962); Bendix & Bøgevig (1998a, 1998b); Hawthorne et al. (2001); Jørgensen (1957); Mustafi & Makinen (1988); Mustafi et al. (1999); Nugent & Mayer (1988); Palma-Vittorelli, Palma, Palumbo & Sgarlata (1956); Seifert & Uebach (1981); Smith, LoBrutto & Pecoraro (2002); Tézé et al. (2000); Tachez & Théobald (1980); Willigen et al. (1982).

S2. Experimental

A solution of vanadylsulfate was treated with a solution of bariumtriflate (quantities of reagents?). The resulting precipitate of bariumsulfate was removed by filtration. The filtrate was concentrated by rotary evaporation and left in a desicator for several weeks to form crystals of few centimetres in size. From one of these very hygroscopic crystals, a piece suitable for X-ray diffraction was cut under an atmosphere of dry dinitrogen.

S3. Refinement

During the refinement of the title complex, the –CF₃ group on one of the trifluoromethanesulfonate anions was found to be disordered. The large ADP for the C1F11₂F12 unit suggests disorder due to rotation of the –CF₃ group. The disorder was resolved by refining the F11 atom in two positions.

The large R_int value is propably caused by slow decay of the crystal due to the highly hygroscopic nature of the title compound.

Computing details

Data collection: COLLECT (Nonius, 1999); cell refinement: DIRAX (Duisenberg, 1992); data reduction: EVALCCD (Duisenberg, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97.

Figures

Figure 1. Molecular structure of the cation [VO(H2O)5]^2+., Figure 2. Packing and hydrogen bonding in [V(O)(H2O)5](CF3SO3)2.

Pentaaquaoxovanadium(IV) trifluoromethanesulfonate

Crystal data

[VO(H2O)5](CF3SO3)2	F(000) = 454
Mr = 455.16	Dx = 2.017 Mg m^−3
Monoclinic, P21/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yb	Cell parameters from 11327 reflections
a = 9.688 (2) Å	θ = 2.0–26.0°
b = 7.7579 (17) Å	µ = 1.07 mm^−1
c = 10.219 (4) Å	T = 122 K
β = 102.684 (19)°	Prism, blue
V = 749.3 (4) Å^3	0.43 × 0.26 × 0.26 mm
Z = 2

Data collection

Nonius KappaCCD area-detector diffractometer	1588 independent reflections
Radiation source: fine-focus sealed tube	1429 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.141
ω and ϕ scans	θmax = 26.0°, θmin = 2.0°
Absorption correction: integration Gaussian integration (Coppens, 1970)	h = −11→11
Tmin = 0.747, Tmax = 0.843	k = −9→9
18866 measured reflections	l = −12→12

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)] = 0.038	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.104	H-atom parameters constrained
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0498P)^2 + 0.7459P] where P = (Fo^2 + 2Fc^2)/3
1588 reflections	(Δ/σ)max < 0.001
131 parameters	Δρmax = 0.48 e Å^−3
4 restraints	Δρmin = −0.56 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.

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

8.6335 (0.0048) x + 0.0000 (0.0000) y + 2.5236 (0.0076) z = 1.9629 (0.0013)

* 0.0000 (0.0000) O3 * 0.0000 (0.0000) O4 * 0.0000 (0.0000) O3_$1 * 0.0000 (0.0000) O4_$1 - 0.2880 (0.0012) V

Rms deviation of fitted atoms = 0.0000

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	Occ. (<1)
V	0.17902 (5)	0.2500	0.05125 (6)	0.0193 (2)
O1	0.0193 (2)	0.2500	−0.0267 (3)	0.0294 (6)
O2	0.4049 (2)	0.2500	0.1391 (3)	0.0244 (5)
H2	0.4602	0.3407	0.1490	0.029*
O3	0.17120 (15)	0.4314 (2)	0.19209 (18)	0.0257 (4)
H3A	0.1910	0.5443	0.1871	0.031*
H3B	0.1126	0.4263	0.2399	0.031*
O4	0.24447 (15)	0.0615 (2)	−0.05857 (17)	0.0259 (4)
H4A	0.1860	0.0290	−0.1326	0.031*
H4B	0.3325	0.0635	−0.0728	0.031*
C1	0.5576 (5)	0.7500	0.3632 (5)	0.0636 (16)
F11	0.5170 (19)	0.849 (3)	0.4427 (13)	0.098 (5)	0.43 (3)
F12	0.6941 (3)	0.7500	0.3650 (4)	0.0823 (11)
F11A	0.5340 (12)	0.914 (3)	0.4100 (17)	0.095 (4)	0.57 (3)
S1	0.45741 (8)	0.7500	0.19089 (10)	0.0230 (2)
O11	0.50218 (17)	0.5942 (2)	0.1362 (2)	0.0339 (5)
O12	0.3103 (2)	0.7500	0.1998 (3)	0.0295 (6)
C2	−0.1222 (4)	0.2500	0.4869 (4)	0.0281 (8)
F21	−0.18113 (17)	0.3884 (2)	0.52622 (16)	0.0421 (4)
F22	0.0143 (2)	0.2500	0.5438 (2)	0.0415 (6)
S2	−0.14717 (7)	0.2500	0.30406 (8)	0.0188 (2)
O21	−0.07609 (15)	0.4061 (2)	0.27632 (17)	0.0249 (4)
O22	−0.2970 (2)	0.2500	0.2535 (3)	0.0273 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
V	0.0063 (3)	0.0226 (4)	0.0303 (4)	0.000	0.0070 (2)	0.000
O1	0.0097 (11)	0.0363 (15)	0.0427 (16)	0.000	0.0072 (10)	0.000
O2	0.0079 (10)	0.0231 (13)	0.0427 (15)	0.000	0.0065 (10)	0.000
O3	0.0165 (8)	0.0232 (9)	0.0424 (11)	−0.0015 (7)	0.0175 (7)	−0.0029 (8)
O4	0.0107 (7)	0.0335 (10)	0.0352 (10)	−0.0044 (7)	0.0089 (7)	−0.0099 (8)
C1	0.037 (3)	0.109 (5)	0.044 (3)	0.000	0.005 (2)	0.000
F11	0.074 (7)	0.180 (14)	0.038 (4)	0.030 (7)	0.009 (3)	−0.019 (5)
F12	0.0268 (13)	0.128 (3)	0.079 (2)	0.000	−0.0155 (14)	0.000
F11A	0.082 (4)	0.139 (8)	0.069 (6)	−0.028 (5)	0.025 (4)	−0.066 (6)
S1	0.0103 (4)	0.0226 (5)	0.0387 (5)	0.000	0.0107 (3)	0.000
O11	0.0162 (8)	0.0245 (10)	0.0661 (14)	−0.0010 (7)	0.0202 (8)	−0.0034 (9)
O12	0.0132 (11)	0.0258 (13)	0.0552 (17)	0.000	0.0195 (11)	0.000
C2	0.0218 (17)	0.034 (2)	0.0279 (19)	0.000	0.0048 (14)	0.000
F21	0.0450 (9)	0.0493 (11)	0.0360 (9)	0.0077 (8)	0.0175 (8)	−0.0084 (8)
F22	0.0251 (11)	0.0596 (16)	0.0332 (12)	0.000	−0.0079 (9)	0.000
S2	0.0072 (3)	0.0274 (5)	0.0222 (4)	0.000	0.0039 (3)	0.000
O21	0.0135 (7)	0.0318 (10)	0.0310 (9)	−0.0011 (7)	0.0081 (7)	0.0015 (8)
O22	0.0074 (10)	0.0366 (15)	0.0367 (14)	0.000	0.0023 (10)	0.000

Geometric parameters (Å, º)

V—O1	1.577 (2)	C1—F11A^ii	1.394 (14)
V—O2	2.175 (2)	C1—F11A	1.394 (14)
V—O3	2.0262 (18)	C1—S1	1.814 (5)
V—O4	2.0277 (17)	S1—O11^ii	1.4381 (19)
V—O3^i	2.0262 (18)	S1—O11	1.4382 (19)
V—O4^i	2.0277 (17)	S1—O12	1.448 (2)
O2—H2	0.8768	C2—F21^i	1.319 (3)
O3—H3A	0.9008	C2—F21	1.319 (3)
O3—H3B	0.8276	C2—F22	1.323 (4)
O4—H4A	0.8768	C2—S2	1.830 (4)
O4—H4B	0.8966	S2—O22	1.430 (2)
C1—F11	1.245 (13)	S2—O21	1.4512 (18)
C1—F12	1.318 (5)	S2—O21^i	1.4512 (17)
O1—V—O2	174.23 (12)	F11^ii—C1—F11A	104 (2)
O1—V—O3	99.97 (8)	F12—C1—F11A	103.6 (5)
O1—V—O4	96.43 (8)	F11A^ii—C1—F11A	131.3 (18)
O3—V—O4	163.52 (7)	F11—C1—S1	117.0 (7)
O1—V—O3^i	99.97 (8)	F11^ii—C1—S1	117.0 (7)
O3—V—O3^i	87.98 (10)	F12—C1—S1	109.6 (4)
O1—V—O4^i	96.43 (8)	F11A^ii—C1—S1	103.9 (8)
O3—V—O4^i	87.56 (8)	F11A—C1—S1	103.9 (8)
O3^i—V—O4^i	163.52 (7)	C1—F11—F11^ii	51.8 (12)
O3^i—V—O4	87.56 (8)	O11^ii—S1—O11	114.43 (15)
O4^i—V—O4	92.28 (10)	O11^ii—S1—O12	114.17 (8)
O3—V—O2	84.15 (7)	O11—S1—O12	114.17 (8)
O3^i—V—O2	84.15 (7)	O11^ii—S1—C1	103.54 (12)
O4^i—V—O2	79.62 (7)	O11—S1—C1	103.54 (12)
O4—V—O2	79.62 (7)	O12—S1—C1	105.3 (2)
V—O2—H2	125.6	F21^i—C2—F21	108.9 (3)
V—O3—H3A	126.4	F21^i—C2—F22	108.9 (2)
V—O3—H3B	121.6	F21—C2—F22	108.9 (2)
H3A—O3—H3B	105.2	F21^i—C2—S2	110.01 (19)
V—O4—H4A	117.7	F21—C2—S2	110.01 (19)
V—O4—H4B	120.1	F22—C2—S2	110.1 (2)
H4A—O4—H4B	108.8	O22—S2—O21	114.64 (8)
F11—C1—F11^ii	76 (2)	O22—S2—O21^i	114.64 (8)
F11—C1—F12	116.8 (10)	O21—S2—O21^i	113.08 (13)
F11^ii—C1—F12	116.8 (10)	O22—S2—C2	105.37 (15)
F11—C1—F11A^ii	104 (2)	O21—S2—C2	103.74 (9)
F12—C1—F11A^ii	103.6 (5)	O21^i—S2—C2	103.74 (9)

Symmetry codes: (i) x, −y+1/2, z; (ii) x, −y+3/2, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O11	0.88	2.02	2.834 (2)	154
O3—H3A···O12	0.90	1.96	2.808 (2)	157
O3—H3B···O21	0.83	1.95	2.725 (2)	156
O4—H4B···O11^iii	0.90	1.87	2.752 (2)	168
O4—H4A···O21^iv	0.88	1.87	2.734 (2)	166

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