Acta Chim. Slov. 2002, 49, 259-265. 259 SYNTHESIS AND CRYSTAL STRUCTURE OF LUTIDINIUM AQUAFLUOROOXOVANADATE(IV)† Alojz Demšar,* Ivan Leban Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerceva 5, SI-1000 Ljubljana, Slovenia Gerald Giester Institut for Mineralogy and Crystallography, University of Vienna, Althannstrasse 14, A-1090 Vienna, Austria † This paper is dedicated to Dr. Karel Lutar Received 16-04-2002 Abstract The complex (LutH)2[V2F6O2(H2O)2] was prepared from aqueous HF solution of VO2+ and lutidine. The X-ray structure revealed dimeric anions connected to the chain by hydrogen bonds. The effect of the cation and intraionic hydrogen bonds on the stability of the bioctahedral anion is discussed. Introduction Structures of fluorides and fluorometallates of 3d transition metals and smaller main group metals (Li, Na, Mg, Al) relate with a few exceptions to the arrangement of octahedra. The octahedra are in most cases either isolated or connected into chains, sheets or three-dimensional networks. Fewer are oligomers built from two to five octahedra.1 For example, the edge-shared bioctahedral unit was reported only recently in (PyH)4[Al2F10].2 The structures of metallic oxofluorides and oxofluoometallates as well as aquafluorometallates resemble the structures of fluorides and fluorometallates due to similar size of fluorine and oxygen atoms. The bioctahedral edge-shared unit with two metal-fluorine-metal bridges was found in structures of (R4N)2[M2F8(H2O)2] (R = Me, M = Fe, Al)3-5 and (R4N)2[V2F6O2(H2O)2] (R = Me, Et).6,7 The oligomeric fluorides exhibits interesting magnetic and conductive properties when compared to compounds with isolated octahedra or polymeric structures.1,8 In addition, the dehydration of [(CH3)4N]2[Al2F8(H2O)2] afforded (CH3)4N[AlF4] as the first tetrahedral fluoroaluminate.3,5 Thermal decomposition of this compounds resulted in a new, porous polymorph of aluminum fluoride.9,10 Herein, we report the synthesis and characterization, including X-ray structure of (LutH)2[V2F6O2(H2O)2] 1 (Lut = lutidine, A. Demšar, I. Leban, G. Giester: Synthesis and crystal structure of lutidinium aquafluorooxovanadate... 260 Acta Chim. Slov. 2002, 49, 259-265. 2,6-dimethylpyridine). The role of cation on the formation of the bioctahedral unit is discussed. Results and discussion The compound 1 crystallizes as blue crystals from the solution of VO2+ in 10% aqueous HF after addition of lutidine (lutidine : VO2+ mol ratio was 5:1). The X-ray structure determination shows bioctahedral anions [V2F6O2(H2O)2]2- connected into chains by fluorine-water hydrogen bonds (Figure 1, Tables 1 and 2). Lutidinium cation is hydrogen-bonded to the terminal fluorine atom of the anion. The structure of anion is similar to the structure of anion found in (R4N)2[V2F6O2(H2O)2] (R = Me, Et).6,7 Vanadium atom is six-coordinated by two terminal and two bridging fluorine atoms, oxygen atom (oxo ligand) and water molecule. Two bridging fluorine atoms are at distances of 1.938(1) and 2.189(1) Å with the longer distance in trans position to oxo ligand. All water hydrogen atoms form strong hydrogen bonds. There are two intraionic hydrogen bonds within [V2F6O2(H2O)2]2- with the distance F(3)···H(12)-O(2) 2.670(2) Å and angle 158(3)º. The distances F(3)···H(12) and H(12)-O(2) are 1.80(4) and 0.91(4) Å, respectively. The hydrogen bond energy of 29 kJ mol-1 was estimated from IR spectra for analogous hydrogen bond (distance 2.686 Å) in [(CH3)4N]2[V2F6O2(H2O)2].6 The dissociation of [(C5Me5)4Ti4F13Li] with the cleavage Figure 1. Molecular structure of (LutH)2[V2F6O2(H2O)2] 1. A. Demšar, I. Leban, G. Giester: Synthesis and crystal structure of lutidinium aquafluorooxovanadate... Acta Chim. Slov. 2002, 49, 259-265. 261 of two Ti(IV)-F-Ti(IV) bridging bonds is endothermic at 75 kJ mol-1.11 We used these values for a rough evaluation of bonding energies within bioctahedral anion in 1. The contribution of two hydrogen bonds (58 kJ mol-1) seems comparable to the contribution of two V(IV)-F-V(IV) bridging bonds (75 kJ mol-1). Therefore the intraionic hydrogen bonds in [V2F6O2(H2O)2]2- are likely important for stability of this bioctahedral anion. However, the dehydration of [(CH3)4N]2[V2F6O2(H2O)2] leaves anhydrous product with [VOF3]- anions coupled to some extend and with no center of symmetry.6 On the other hand, the dehydration of [(CH3)4N]2[Al2F8(H2O)2] resulted in free tetrahedral [AlF4]-anions.3,5 This anion was also observed by 19F NMR spectroscopy in acetonitrile solution of [(CH3)4N]2[Al2F8(H2O)2].5 The hydrogen bonds connecting anions [V2F6O2(H2O)2]2- to the chain are very short and nearly linear. The distance F(2)···H(11)-O(2) is 2.607(2) Å and the angle is 167(3)º. The hydrogen atom is at distances F(2)···H(11) 1.93(3) Å and H(11)-O(2) 0.69(4) Å. However much shorter intraionic hydrogen bond of coordinated fluorine to water of 2.437 Å was found in dicobalt pyrazolate complex.12 The lutidinium cation forms a hydrogen bond to terminal fluorine with distance of 2.775(2) Å. The lutidinium-fluorine hydrogen bond does not alter the pattern of intra- and interionic hydrogen bonding in 1 in comparison to bioctahedral aquafluorometallates with tetraalkylammmonium cations.6,7 We can conclude that interaction of coordinated fluorines and cations are very weak in aquafluorometallates with large tetraalkylammonium and lutidinium cations. Consequently all the coordinated fluorines could be strong acceptors of hydrogen bonds from coordinated water molecules. This intra- and interionic hydrogen bond network likely stabilizes the bioctahedral unit in 1 and in related aquafluorometalates. The IR spectrum of 1 shows very broad absorption of stretching vibrations of the N-H and O-H bonds from 3000 to 3300 cm-1 and terminal fluorine stretching vibrations at 500 cm-1. The V=O stretching appears at 976 cm-1 characteristic for oxo ligand not involved in hydrogen bond.6, 13 The absorptions of lutidinium cation are at expected frequencies. A. Demšar, I. Leban, G. Giester: Synthesis and crystal structure of lutidinium aquafluorooxovanadate... 262 Acta Chim. Slov. 2002, 49, 259-265. Table 1. Final Coordinates and Equivalent Isotropic Displacement Parameters of the non-Hydrogen atoms for 1 x/a y/b z/c Ueq VI 0.20690(4) 0.94195(3) 0.90077(3) 0.0304(1) Fl 0.04028(13) 0.91761(12) 1.13053(10) 0.0340(3) F2 0.40124(14) 0.80220(13) 1.02156(12) 0.0393(3) F3 0.09366(16) 0.74797(13) 0.91117(13) 0.0457(3) Ol 0.3213(2) 0.9753(2) 0.73121(15) 0.0513(4) 02 0.2586(2) 1.15640(18) 0.95100(17) 0.0405(4) Nl 0.7279(2) 0.35434(19) 0.67548(17) 0.0375(4) Cl 0.7526(3) 0.2760(2) 0.5609(2) 0.0402(5) C2 0.7762(3) 0.3776(3) 0.4122(2) 0.0547(7) C3 0.7731(4) 0.5509(3) 0.3869(3) 0.0636(8) C4 0.7473(4) 0.6234(3) 0.5077(3) 0.0588(7) C5 0.7254(3) 0.5227(2) 0.6557(2) 0.0465(6) C6 0.7515(5) 0.0893(3) 0.6028(3) 0.0554(8) C7 0.7008(6) 0.5868(4) 0.7960(4) 0.0756(12) Ueq = 1/3 of the trace of the orthogonalized U Tensor Table 2. Selected Bond Lengths (Å) and Angles (deg) for 1 Vl-Fl 2.1893(11) F2-V1-F3 92.22(6) V1-F2 1.9339(12) F2-V1-01 102.47(7) V1-F3 1.9103(12) F2-V1-02 89.60(6) Vl-Ol 1.5883(14) Fl(a)-Vl-F2 155.05(5) Vl-02 2.0708(16) F3-V1-01 101.14(7) Vl-Fl(a) 1.9380(11) F3-V1-02 160.91(6) Nl-Hl 0.78(3) Fl(a)-Vl-F3 88.01(6) F1-V1-F2 80.64(5) Ol-Vl-02 97.01(8) F1-V1-F3 81.91(5) Fl(a)-Vl-01 101.96(7) Fl-Vl-Ol 175.48(7) Fl(a)-Vl-02 82.45(6) Fl-Vl-02 79.64(6) VI-Fl-VI (a) 105.31(5) F1-VI -F1(a) 74.69(5) The thermal decomposition proceeds in four overlapping steps with mass loss 15.2, 25.9, 8.6 and 16.6% in corresponding temperature ranges 100-160 ºC, 160-220 ºC, 220-330 ºC and 330-580 ºC. No stable intermediate was observed in thermogravimetric curve and no stoichometry of decomposition could be proposed from mass loss. A. Demšar, I. Leban, G. Giester: Synthesis and crystal structure of lutidinium aquafluorooxovanadate... Acta Chim. Slov. 2002, 49, 259-265. 263 Experimental General Considerations. Infrared spectra (Nujol) were recorded on a Perkin-Elmer FT-1720X spectrometer. Elemental analyses were carried out on Perkin-Elmer 2400 CHN analyser at the University of Ljubljana (Department of Organic Chemistry). Thermogravimetric analysis was done on a Mettler 2000C in the atmosphere of argon. Table 3. Crystalographic Data for 1 Chemical formula C14H24F6N2O4V2 Molecular weight 500.23 Crystal system Triclinic Space group P1-(No. 2) a(Å) 7.1910(10) b(Å) 8.253(2) c(Å) 9.195(2) 2.0a(I)] Numbers of par. 176 R (observed) 0.0279 wR2 (obs.) 0.0760 S 1.08 Largest difference peak and -0.35, 0.26 hole(eÅ-3) R=3(|Fo|-|Fc|)/3|Fo|. wR2=(3[w(Fo2-Fc2)2]/3(wFo2)2)1/2. (LutH)2[V2F602(H20)2] 1. Vanadium pentaoxide (5 mmol, 0.94 g) was dissolved in 40 mL of 10 % HF in Teflon becher. Gaseous SO2 was bubbled into solution for 20 min. The solution was heated on a water bath for 0.5 h, cooled to room temperature and 2,6-dimethylpyridine (50 mmol, 5,3 g) was added. The blue crystals of 1 appeared in 5 days. The crystals were filtered and washed with acetone. Yield 2.3 g (46%). Anal. A. Demšar, I. Leban, G. Giester: Synthesis and crystal structure of lutidinium aquafluorooxovanadate... 264 Acta Chim. Slov. 2002, 49, 259-265. Calculated for C14H24F6N2O4V2: C, 33.62; H, 4.84; N, 5.60, V, 20.37. Found: C, 33.27; H, 4.75; N, 5.39; V, 21.0. IR (cm–1, Nujol): 3284, 3180, 3077, 1643, 1625, 1550, 1274, 1180, 1056, 976, 811, 561, 502. X-ray Crystallography. The details of crystal data collection and refinement parameters for (LutH)2[V2F6O2(H2O)2] 1 are listed in Table 1. Data were collected with an Kappa-CCD Nonius diffractometer using graphite monochromated MoKa radiation (? = 0.71073 Å). The structures were solved by direct methods implemented in SHELXS8614 and refined with SHELX97.15 All non-hydrogen atoms were refined anisotropically, the hydrogen atoms were refined isotropically having isotropic displacement parameters taken from those of attached heavy atoms and multiplied by 1.2. Supplementary data (X-ray crystallographic files, in CIF format) are available from the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, on request, quoting the deposition number CCDC 184130 for the structure 1. Acknowledgements This work was supported by the Grant PO-0511-0103 from the Ministry of Education, Science and Sport, Republic of Slovenia. References and Notes 1. Férey, G. R. In Encyclopedia of Inorganic Chemistry; King, R. B., Ed., Wiley, N. Y., 1994, Vol. 7, pp 1207-1223. 2. Adamczyk, B.; Troyanov, S. I.; Schneider, M.; Kemnitz, E. Z. Anorg. Allg. Chem. 2000, 626, 2543-2548. 3. Bukovec, P.; Šiftar, J. Monatsh. Chem. 1975, 106, 483-490. 4. Bentrup, U.; Massa, W. Z. Naturforsch. 1991, B46, 395-399. 5. Herron, N.; Harlow, R. L.; Thorn, D. L. Inorg. Chem. 1993, 32, 2985-2986. 6. Bukovec, P.; Milicev, S.; Demšar, A.; Golic, L. J. Chem. Soc., Dalton Trans. 1981, 1802-1806. 7. Demšar, A.; Bukovec, P. Croat. Chem. Acta 1984, 57, 673-677. 8. Hatfield, W. E.. In Encyclopedia of Inorganic Chemistry; King, R. B., Ed., Wiley, N. Y., 1994, Vol. 4, pp 2049-2065. 9. Bentrup, U. Eur. J. Solid State Inorg. Chem. 1992, 29, 51-61. 10. Herron, N.; Thorn, D. L.; Harlow, R. L.; Jones, G. A.; Parise, J. B.; Fernandezbaca, J. A.; Vogt, T. Chem. Mater. 1995, 7, 75-83. 11. Demšar, A.; Pevec, A.; Golic, L.; Petricek, S.; Petric, A.; Roesky, H. W. Chem. Commun. 1998, 1029-1030. 12. Meyer, F.; Heinze, K.; Nuber, B.; Zsolnai, L. J. Chem. Soc., Dalton Trans. 1998, 207-213. 13. Demšar, A.; Bukovec, P. Inorg. Chim. Acta 1977, 25, L121-L122. 14. Sheldrick, G. M., SHELXS86, Program for the Solution of Crystal Structures, University of Göttingen, Germany, 1986. 15. Sheldrick, G. M., SHELX97, Program for the Refinement of Crystal Structures from Diffraction Data, University of Göttingen, Germany, 1997. A. Demšar, I. Leban, G. Giester: Synthesis and crystal structure of lutidinium aquafluorooxovanadate... Acta Chim. Slov. 2002, 49, 259-265. 265 Povzetek Akvaoksofluorovanadat(IV) (LutH)2[V2F6O2(H2O)2] (Lut = lutidin; 2,6-dimethylpiridin) kristalizira iz raztopine VO2+ in lutidina v 10 % HF. V kristalni strukturi so anioni kot dvojni oktaedri, povezani preko skupnega roba in z dvema vodikovima vezema. Vodikove vezi povezujejo anione v verigo. A. Demšar, I. Leban, G. Giester: Synthesis and crystal structure of lutidinium aquafluorooxovanadate...