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Conversion of thorium(IV) oxide into thorium(IV) trifluoromethanesulfonate: Crystal structure of thorium(IV) trifluoromethanesulfonate dihydrate
Inorganic Chemistry Communications 24 (2012) 234–236
Contents lists available at SciVerse ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Conversion of thorium(IV) oxide into thorium(IV) trifluoromethanesulfonate: Crystal structure of thorium(IV) trifluoromethanesulfonate dihydrate Krzysztof Lyczko a,⁎, Monika Lyczko a, Marta Walo a, Janusz Lipkowski b a b
Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw, Poland Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
a r t i c l e
i n f o
Article history: Received 11 March 2012 Accepted 9 July 2012 Available online 20 July 2012 Keywords: Thorium(IV) triflate Crystal structure Thorium(IV) oxide solubility
a b s t r a c t The conversion of thorium(IV) oxide into thorium(IV) trifluoromethanesulfonate (triflate) in the concentrated aqueous solution of trifluoromethanesulfonic (triflic) acid under reflux condition was presented as a new simple method for dissolution of ThO2. In this method after refluxing and subsequent evaporation of water and triflic acid two forms of very hygroscopic solid thorium(IV) triflate salt were obtained: a greyish-white powder containing small amounts of triflic acid (with approximate composition of Th(CF3SO3)4·0.1CF3SO3H·2H2O, estimated by the TGA method), and colourless crystals of the [Th(CF3SO3)4(H2O)2]n formula. The last form has a polymeric structure in which thorium(IV) ion is surrounded by seven oxygen atoms from seven triflate ions and by two oxygen atoms from two water molecules, forming the ThO9 core with Th\O bond lengths in the range 2.371–2.516(3)Å. Thermal decomposition of both thorium(IV) triflate forms have led mainly to the formation of ThO2, which was confirmed by means of FIR, PXRD and XPS techniques. © 2012 Elsevier B.V. All rights reserved.
The interest in the thorium–uranium fuel cycle, in which thorium232 (a fertile material) irradiated by neutrons is transformed into uranium-233 (a fissile material), recently revived. In the case of nuclear power reactors using thorium(IV) oxide as a source of fuel the study on methods of its recovery is very important. Because of this, the solubility problem of thorium(IV) oxide is of considerable significance. It is commonly known that ThO2 is chemically stable. In aqueous solution it dissolves in concentrated nitric acid, only in the presence of small amounts of fluoride ions as a catalyst [1,2]. The most widespread method for dissolution of thorium(IV) oxide from nuclear fuel is its reaction with the so called Thorex solution consisting of 13 M HNO3, 0.02–0.05 M HF and 0.1 M Al(NO3)3 [1,2]. The last component protects from the corrosive action of hydrofluoric acid and simultaneously prevents precipitation of thorium(IV) fluoride. A solid state reaction method involving sintering of thorium(IV) oxide with ammonium sulphate at temperatures of 250, 365 and 450 °C, which leads to the formation of (NH4)4Th(SO4)4, (NH4)2Th(SO4)3 and Th(SO4)2 compounds, respectively, was also suggested as a way to synthesise well soluble thorium salts [3]. In this paper we report another simple route for dissolution of thorium(IV) oxide. We found that chemically inert ThO2 readily dissolves in the concentrated aqueous solution of trifluoromethanesulfonic (triflic) acid under reflux [4]. After dissolution the excess water and acid were
⁎ Corresponding author. Tel.: +48 22 5041051; fax: +48 22 8111917. E-mail address: [email protected] (K. Lyczko). 1387-7003/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2012.07.024
evaporated at 170 °C in an oven, and after 5 days a dry greyish-white powder together with some colourless crystals was unexpectedly formed [5]. Because of their hygroscopic properties, the compounds had to be stored in an airtight vessel in a desiccator. The methods of the synthesis of thorium(IV) triflate in the reaction of triflic acid with thorium(IV) nitrate [6] or with thorium(IV) hydroxide (precipitated from thorium(IV) nitrate by sodium hydroxide) were described earlier [7]. X-ray crystallography [8] shows that crystals obtained in this work have a polymeric structure with the [Th(CF3SO3)4(H2O)2] fragment repeated in the chain (Fig. 1). The thorium(IV) ion is surrounded by nine oxygen atoms. Seven of them belong to triflate ions with Th\O bond lengths in the range 2.371(3)–2.474(3) Å (mean 2.42 Å), and two to water molecules with Th\O bond distances 2.452(4) and 2.516(3) Å (mean 2.48 Å). The coordination polyhedron around the metal centre can be considered as a square antiprism with additional water molecule, with the longest Th\O bond distance, in the capping position. Most of triflate ions in this structure act as bridging groups between two neighbouring thorium atoms. Persson and co-workers [9] have recently obtained crystals of the H5O2[Th(H2O)6(CF3SO3)3] [Th(H2O)3(CF3SO3)6] formula from concentrated aqueous triflic acid solution of thorium(IV) ions stored in a refrigerator. In this structure thorium(IV) ions are involved in the formation of independent cationic and anionic units, and the aquaoxonium ion forms a bridge between them through hydrogen bonds. The arrangement of nine oxygen donor atoms around both thorium(IV) ions shows the monocapped square antiprismatic and tricapped trigonal prismatic configurations for the cation and the anion, respectively. More water molecules in
K. Lyczko et al. / Inorganic Chemistry Communications 24 (2012) 234–236
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Fig. 1. Fragment of the crystal structure of [Th(CF3SO3)4(H2O)2]n: (a) with some atom labelling. The Th\O bond lengths (Å) are as follows: Th1-O10 2.371(3), Th1-O4 2.418(3), Th1-O7 2.421(3), Th1-O6′ 2.425(3), Th1-O3′ 2.427(3), Th1-O1 2.433(3), Th1-O13 2.452(4), Th1-O9′ 2.474(3), Th1-O14 2.516(3) [symmetry codes: (′) x, −y+ 0.5, z − 0.5; (″) x, −y+ 0.5, z + 0.5]. (b) With the non-hydrogen atoms as the 30% probability ellipsoids showing the modelled disorder in the triflate ions.
the first coordination sphere of thorium(IV) ion were present only in the crystal structures of complexes: [Th(H2O)7(C5O5)] [10], [Th((H2O)7 (OH)](C2N8)2(C2N8H)2·10H2O [11], [Th(H2O)8(ClO4)](ClO4)3·H2O [9] and [Th(H2O)10]Br4 [12]. The TGA studies on crystals of [Th(CF3SO3)4(H2O)2]n and on the greyish-white solid of thorium(IV) triflate were performed under nitrogen and under air atmosphere in the range from 30 to 800 °C. As shown in Fig. 2, the decomposition process is different for powdery and for crystalline form, but is identical in the case of both atmospheres used for the respective form. Both forms of the studied compound are stable up to 200 °C. The sharp weight loss above 250 °C corresponds to the decomposition of thorium(IV) compound, and the remaining weight of about 31% at temperature 800 °C is mainly due to formation of ThO2. The presence of ThO2 was confirmed by far infrared (FIR), powder X-ray diffraction (PXRD) and X-ray photoelectron spectroscopy (XPS) techniques [13]. XPS analysis of decomposition products has shown the highest concentration of thorium (>21 at.%) and oxygen (> 57 at.%). The gradual weight losses of water (at 120 °C) and triflic acid (at 178 °C) were observed for the
Fig. 2. TGA curves for crystalline (1) and for greyish-white solid form (2) of thorium(IV) triflate under nitrogen (solid lines) and under air (dashed lines) atmosphere.
greyish-white solid form of the studied compound. Such behaviour means that this form still contains some unevaporated CF3SO3H acid and water molecules [14]. On the other hand, such loss of triflic acid and water was not registered for [Th(CF3SO3)4(H2O)2]n crystals. The Th–O vibrations in thorium(IV) oxide were recognised in the far infrared region. This type of vibrations was found in previous studies [15] as a very broad band at 310 or 365 cm −1. In our work the most intensive band with maximum of absorption lying in the range 355–335 cm −1 for ThO2 is, after sintering at 800 °C (Fig. 3), shifted to a bit lower wave number of around 340–320 cm −1. The same position of the main band as that for sintered thorium(IV) oxide is observed in the case of products obtained after decomposition of thorium(IV) triflate. Moreover, instead of a weak but well separated band around 520 cm −1 for pure thorium(IV) oxide a broad shoulder in the range 550–400 cm −1, originating from decomposition products, has been found. Powder X-ray diffraction studies (Figs. S3–5) have confirmed that thorium(IV) oxide is the main product obtained
Fig. 3. FIR spectra of ThO2 (1), sintered ThO2 at 800 °C (2) and products obtained after decomposition of greyish-white solid form of thorium(IV) triflate at 800 °C under nitrogen (3) and under air (4) atmospheres (the same spectra were registered after decomposition of crystalline thorium(IV) triflate).
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after thermal decomposition of thorium(IV) triflate under both atmospheres used. However, comparing these data with the available PXRD patterns of inorganic thorium(IV) compounds [16], the formation of smaller amounts of thorium(IV) oxyfluoride and thorium(IV) fluoride is also observed during decomposition of thorium(IV) triflate under nitrogen atmosphere whereas under air atmosphere the first of them is only noticed. Previously, it appeared that the thermal decomposition of lanthanoid trifluoromethanesulfonate salts results in the formation of fluorides [17]. In conclusion, our investigation shows that there is a new simple method for dissolution of thorium(IV) oxide by refluxing this compound with a concentrated aqueous solution of triflic acid. It is interesting to note that during evaporation of water and excess triflic acid from the aqueous thorium(IV) triflate solution the colourless polymeric [Th(CF3SO3)4(H2O)2]n compound crystallises. Besides crystals, a greyish-white solid form of thorium(IV) triflate, containing additionally small amount of triflic acid, is obtained.
[6] [7] [8]
[9]
Acknowledgements [10]
This work was financed by the Operational Program Innovate Economy and supported by the European Regional Development Fund (project POIG 01.03.01-00-076/08-00 “Analysis of thorium use in nuclear power plant”).
[11]
[12]
Appendix A. Supplementary material
[13]
Crystallographic data have been deposited with the Cambridge Crystallographic Data Centre, under deposition number CCDC 868843. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/ cif. Supplementary data to this article can be found online at http:// dx.doi.org/10.1016/j.inoche.2012.07.024.
[14]
[15]
References [16] [1] T. Takeuchi, C.K. Hanson, M.E. Wadsworth, Kinetics and mechanism of the dissolution of thorium oxide in hydrofluoric acid and nitric acid mixtures, J. Inorg. Nucl. Chem. 33 (1971) 1089–1098. [2] M. Akabori, T. Shiratori, Dissolution of ThO2-based oxides in nitric acid solutions at elevated temperatures, J. Nucl. Sci. Technol. 31 (1994) 539–545. [3] S. Chaudhury, M. Keskar, A.V. Patil, K.D.S. Mudher, V. Venugopal, Studies on the dissolution behaviour of ThO2 and (U, Th)O2 by a solid state reaction method, Radiochim. Acta 94 (2006) 357–361. [4] Dissolution of thorium(IV) oxide: To a powdered ThO2 (100 mg, 0.379 mmol, 99.9% Matthey Reagent) 0.5 mL water and 2.5 mL trifluoromethanesulfonic (triflic) acid (98% Fluka) were added. The mixture was heated under reflux in a small round-bottomed flask. During this time the temperature at the bottom of the flask was maintained in the range 170–190 °C. After about 10 min a clear slightly pink liquid phase containing aqueous solution of thorium(IV) triflate was obtained. This method was the subject of Polish and European patent application in 2010 and 2011, respectively. [5] IR data (KBr pellet, cm−1): 3500-3300(vs, vbr) νs(OH), 1626(m) δ(HOH), 1275(sh) νas(SO3), 1250(vs) νs(CF3), 1176(m) νas(CF3), 1048(sh), 1033(s) νs(SO3), 767(vw)
[17]
[18]
σs(CF3), 655(m) σs(SO3), 580(vw) σas(CF3), 521(w) σas(SO3) (the same spectra were registered for both forms of thorium(IV) triflate, see also supplementary material); assignments based on [18]. M. Bouby, I. Billard, J. MacCordick, Complexation of Th(IV) with the siderophore pyoverdine A, J. Alloys Compd. 271–273 (1998) 206–210. M. Walker, Process for the preparation of aryl ketones generating reduced amounts of toxic byproducts, US Patent 6362375 (2002). Crystal data for [Th(CF3SO3)4(H2O)2]n: C4H4F12O14S4Th, FW = 864.35, monoclinic, space group P 21/c, a = 10.7700(2) Å, b = 18.4270(2) Å, c = 10.9038(2) Å, β = 103.643(2)° V= 2102.90(6) Å3, Z = 4, Dc = 2.730 g/cm3, μ = 7.656 mm −1, F(000) = 1608, 18626 reflections collected, 5017 unique (Rint = 0.0444), Data/ restraints/parameters: 5017/1/431, GOF = 1.062, final R indices [I> 2σ(I)]: R1 = 0.0285, wR2 = 0.0639, R indices (all data): R1 = 0.0367, wR2 = 0.0679, largest difference peak and hole: 2.32 and −1.59 (0.96 and 1.35 Å from Th1) e·A-3. The single-crystal X-ray diffraction measurement was carried out at 100(2) K on an Agilent Technologies SuperNova (Dual) Eos CCD diffractometer with MoKα radiation (λ=0.71073 Å). The structure was solved by direct methods and refined with full-matrix least-squares technique using SHELXTL program package. All non-hydrogen atoms were refined anisotropically. The hydrogen atoms were placed in calculated positions and refined as riding atoms with common fixed isotropic thermal factors. Analytical numeric absorption correction was applied using CrysAlisPro program. N. Torapava, I. Persson, L. Eriksson, D. Lundberg, Hydration and hydrolysis of thorium(IV) in aqueous solution and the structures of two crystalline thorium(IV) hydrates, Inorg. Chem. 48 (2009) 11712–11723. C. Brouca-Cabarrecq, J.-C. Trombe, f Element croconates 2. Thorium(IV) and dioxouranium(VI) croconates — synthesis, crystal structure and thermal behaviour, Inorg. Chim. Acta 191 (1992) 241–248. R.W.H. Pohl, J. Wiebke, A. Klein, M. Dolg, N. Maggiarosa, A new 5,5′-bitetrazole thorium(IV) compound: synthesis, crystal structure and quantum chemical investigation, Eur. J. Inorg. Chem. (2009) 2472–2476. R.E. Wilson, S. Skanthakumar, P.C. Burns, L. Soderholm, Angew. Chem. Int. Ed. 46 (2007) 8043–8045. The XPS data for samples obtained from decomposition of greyish-white solid form of thorium(IV) triflate: a) under nitrogen atmosphere (in at.%): O (57.2), Th (25.8), F (9.4), C (6.8), and b) under air atmosphere (in at.%): O (58.9), Th (21.7), C (9.8), S (6.8), F (2.1) (only elements with content above 1 at.% are mentioned). All XPS spectra were recorded on a PHI 5000 Versa Probe spectrometer using monochromatic Al Kα radiation. On the base of TGA curves we have estimated a composition of a greyish-white solid form of thorium(IV) triflate as Th(CF3SO3)4·0.1CF3SO3H·2H2O assuming that the whole amount of the studied compound decomposed to ThO2. (a) N.T. McDevitt, W.L. Baun, Infrared absorption study of metal oxides in the low frequency region (700–240 cm−1), Spectrochim. Acta 20 (1964) 799–808; (b) M. Terada, M. Tsuboi, Infrared-active lattice vibrations in a few fluorite-type crystals, Bull. Chem. Soc. Jpn. 37 (1964) 1080–1081. (a) The International Centre for Diffraction Data (ICDD), Powder Diffraction File database. (b) A. Rhandour, J.-M. Reau, S. Matar, P. Hagenmuller, Influence de l'oxygène sur les propriétés cristallographiques et électriques des materiaux de type tysonite, J. Solid State Chem. 64 (1986) 206–216; (c) T.K. Keenan and L.B. Asprey, Lattice constants of actinide tetrafluorides including berkelium, Inorg. Chem. 8 (1960) 235–238. (d) W.H. Zachariasen, Crystal chemical studies of the 5f-series of elements. XIII. The crystal structure of U2F9 and NaTh2F9, Acta Cryst. 2 (1949) 390–393. (a) N. Yanagihara, S. Nakamura, M. Nakayama, Thermal study of several lanthanide triflates, Polyhedron 17 (1998) 3625–3631; (b) K. Egashira, Y. Yoshimura, H. Kanno, Y. Suzuki, TG-DTA study on the lanthanoid trifluoromethanesulfonate complexes, J. Therm. Anal. Calorim. 71 (2003) 501–508. D.H. Johnston, D.F. Shiver, Vibrational study of the trifluoromethanesulfonate anion: unambiguous assignment of the asymmetric stretching modes, Inorg. Chem. 32 (1993) 1045–1047.
Contents lists available at SciVerse ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Conversion of thorium(IV) oxide into thorium(IV) trifluoromethanesulfonate: Crystal structure of thorium(IV) trifluoromethanesulfonate dihydrate Krzysztof Lyczko a,⁎, Monika Lyczko a, Marta Walo a, Janusz Lipkowski b a b
Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw, Poland Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
a r t i c l e
i n f o
Article history: Received 11 March 2012 Accepted 9 July 2012 Available online 20 July 2012 Keywords: Thorium(IV) triflate Crystal structure Thorium(IV) oxide solubility
a b s t r a c t The conversion of thorium(IV) oxide into thorium(IV) trifluoromethanesulfonate (triflate) in the concentrated aqueous solution of trifluoromethanesulfonic (triflic) acid under reflux condition was presented as a new simple method for dissolution of ThO2. In this method after refluxing and subsequent evaporation of water and triflic acid two forms of very hygroscopic solid thorium(IV) triflate salt were obtained: a greyish-white powder containing small amounts of triflic acid (with approximate composition of Th(CF3SO3)4·0.1CF3SO3H·2H2O, estimated by the TGA method), and colourless crystals of the [Th(CF3SO3)4(H2O)2]n formula. The last form has a polymeric structure in which thorium(IV) ion is surrounded by seven oxygen atoms from seven triflate ions and by two oxygen atoms from two water molecules, forming the ThO9 core with Th\O bond lengths in the range 2.371–2.516(3)Å. Thermal decomposition of both thorium(IV) triflate forms have led mainly to the formation of ThO2, which was confirmed by means of FIR, PXRD and XPS techniques. © 2012 Elsevier B.V. All rights reserved.
The interest in the thorium–uranium fuel cycle, in which thorium232 (a fertile material) irradiated by neutrons is transformed into uranium-233 (a fissile material), recently revived. In the case of nuclear power reactors using thorium(IV) oxide as a source of fuel the study on methods of its recovery is very important. Because of this, the solubility problem of thorium(IV) oxide is of considerable significance. It is commonly known that ThO2 is chemically stable. In aqueous solution it dissolves in concentrated nitric acid, only in the presence of small amounts of fluoride ions as a catalyst [1,2]. The most widespread method for dissolution of thorium(IV) oxide from nuclear fuel is its reaction with the so called Thorex solution consisting of 13 M HNO3, 0.02–0.05 M HF and 0.1 M Al(NO3)3 [1,2]. The last component protects from the corrosive action of hydrofluoric acid and simultaneously prevents precipitation of thorium(IV) fluoride. A solid state reaction method involving sintering of thorium(IV) oxide with ammonium sulphate at temperatures of 250, 365 and 450 °C, which leads to the formation of (NH4)4Th(SO4)4, (NH4)2Th(SO4)3 and Th(SO4)2 compounds, respectively, was also suggested as a way to synthesise well soluble thorium salts [3]. In this paper we report another simple route for dissolution of thorium(IV) oxide. We found that chemically inert ThO2 readily dissolves in the concentrated aqueous solution of trifluoromethanesulfonic (triflic) acid under reflux [4]. After dissolution the excess water and acid were
⁎ Corresponding author. Tel.: +48 22 5041051; fax: +48 22 8111917. E-mail address: [email protected] (K. Lyczko). 1387-7003/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2012.07.024
evaporated at 170 °C in an oven, and after 5 days a dry greyish-white powder together with some colourless crystals was unexpectedly formed [5]. Because of their hygroscopic properties, the compounds had to be stored in an airtight vessel in a desiccator. The methods of the synthesis of thorium(IV) triflate in the reaction of triflic acid with thorium(IV) nitrate [6] or with thorium(IV) hydroxide (precipitated from thorium(IV) nitrate by sodium hydroxide) were described earlier [7]. X-ray crystallography [8] shows that crystals obtained in this work have a polymeric structure with the [Th(CF3SO3)4(H2O)2] fragment repeated in the chain (Fig. 1). The thorium(IV) ion is surrounded by nine oxygen atoms. Seven of them belong to triflate ions with Th\O bond lengths in the range 2.371(3)–2.474(3) Å (mean 2.42 Å), and two to water molecules with Th\O bond distances 2.452(4) and 2.516(3) Å (mean 2.48 Å). The coordination polyhedron around the metal centre can be considered as a square antiprism with additional water molecule, with the longest Th\O bond distance, in the capping position. Most of triflate ions in this structure act as bridging groups between two neighbouring thorium atoms. Persson and co-workers [9] have recently obtained crystals of the H5O2[Th(H2O)6(CF3SO3)3] [Th(H2O)3(CF3SO3)6] formula from concentrated aqueous triflic acid solution of thorium(IV) ions stored in a refrigerator. In this structure thorium(IV) ions are involved in the formation of independent cationic and anionic units, and the aquaoxonium ion forms a bridge between them through hydrogen bonds. The arrangement of nine oxygen donor atoms around both thorium(IV) ions shows the monocapped square antiprismatic and tricapped trigonal prismatic configurations for the cation and the anion, respectively. More water molecules in
K. Lyczko et al. / Inorganic Chemistry Communications 24 (2012) 234–236
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Fig. 1. Fragment of the crystal structure of [Th(CF3SO3)4(H2O)2]n: (a) with some atom labelling. The Th\O bond lengths (Å) are as follows: Th1-O10 2.371(3), Th1-O4 2.418(3), Th1-O7 2.421(3), Th1-O6′ 2.425(3), Th1-O3′ 2.427(3), Th1-O1 2.433(3), Th1-O13 2.452(4), Th1-O9′ 2.474(3), Th1-O14 2.516(3) [symmetry codes: (′) x, −y+ 0.5, z − 0.5; (″) x, −y+ 0.5, z + 0.5]. (b) With the non-hydrogen atoms as the 30% probability ellipsoids showing the modelled disorder in the triflate ions.
the first coordination sphere of thorium(IV) ion were present only in the crystal structures of complexes: [Th(H2O)7(C5O5)] [10], [Th((H2O)7 (OH)](C2N8)2(C2N8H)2·10H2O [11], [Th(H2O)8(ClO4)](ClO4)3·H2O [9] and [Th(H2O)10]Br4 [12]. The TGA studies on crystals of [Th(CF3SO3)4(H2O)2]n and on the greyish-white solid of thorium(IV) triflate were performed under nitrogen and under air atmosphere in the range from 30 to 800 °C. As shown in Fig. 2, the decomposition process is different for powdery and for crystalline form, but is identical in the case of both atmospheres used for the respective form. Both forms of the studied compound are stable up to 200 °C. The sharp weight loss above 250 °C corresponds to the decomposition of thorium(IV) compound, and the remaining weight of about 31% at temperature 800 °C is mainly due to formation of ThO2. The presence of ThO2 was confirmed by far infrared (FIR), powder X-ray diffraction (PXRD) and X-ray photoelectron spectroscopy (XPS) techniques [13]. XPS analysis of decomposition products has shown the highest concentration of thorium (>21 at.%) and oxygen (> 57 at.%). The gradual weight losses of water (at 120 °C) and triflic acid (at 178 °C) were observed for the
Fig. 2. TGA curves for crystalline (1) and for greyish-white solid form (2) of thorium(IV) triflate under nitrogen (solid lines) and under air (dashed lines) atmosphere.
greyish-white solid form of the studied compound. Such behaviour means that this form still contains some unevaporated CF3SO3H acid and water molecules [14]. On the other hand, such loss of triflic acid and water was not registered for [Th(CF3SO3)4(H2O)2]n crystals. The Th–O vibrations in thorium(IV) oxide were recognised in the far infrared region. This type of vibrations was found in previous studies [15] as a very broad band at 310 or 365 cm −1. In our work the most intensive band with maximum of absorption lying in the range 355–335 cm −1 for ThO2 is, after sintering at 800 °C (Fig. 3), shifted to a bit lower wave number of around 340–320 cm −1. The same position of the main band as that for sintered thorium(IV) oxide is observed in the case of products obtained after decomposition of thorium(IV) triflate. Moreover, instead of a weak but well separated band around 520 cm −1 for pure thorium(IV) oxide a broad shoulder in the range 550–400 cm −1, originating from decomposition products, has been found. Powder X-ray diffraction studies (Figs. S3–5) have confirmed that thorium(IV) oxide is the main product obtained
Fig. 3. FIR spectra of ThO2 (1), sintered ThO2 at 800 °C (2) and products obtained after decomposition of greyish-white solid form of thorium(IV) triflate at 800 °C under nitrogen (3) and under air (4) atmospheres (the same spectra were registered after decomposition of crystalline thorium(IV) triflate).
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after thermal decomposition of thorium(IV) triflate under both atmospheres used. However, comparing these data with the available PXRD patterns of inorganic thorium(IV) compounds [16], the formation of smaller amounts of thorium(IV) oxyfluoride and thorium(IV) fluoride is also observed during decomposition of thorium(IV) triflate under nitrogen atmosphere whereas under air atmosphere the first of them is only noticed. Previously, it appeared that the thermal decomposition of lanthanoid trifluoromethanesulfonate salts results in the formation of fluorides [17]. In conclusion, our investigation shows that there is a new simple method for dissolution of thorium(IV) oxide by refluxing this compound with a concentrated aqueous solution of triflic acid. It is interesting to note that during evaporation of water and excess triflic acid from the aqueous thorium(IV) triflate solution the colourless polymeric [Th(CF3SO3)4(H2O)2]n compound crystallises. Besides crystals, a greyish-white solid form of thorium(IV) triflate, containing additionally small amount of triflic acid, is obtained.
[6] [7] [8]
[9]
Acknowledgements [10]
This work was financed by the Operational Program Innovate Economy and supported by the European Regional Development Fund (project POIG 01.03.01-00-076/08-00 “Analysis of thorium use in nuclear power plant”).
[11]
[12]
Appendix A. Supplementary material
[13]
Crystallographic data have been deposited with the Cambridge Crystallographic Data Centre, under deposition number CCDC 868843. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/ cif. Supplementary data to this article can be found online at http:// dx.doi.org/10.1016/j.inoche.2012.07.024.
[14]
[15]
References [16] [1] T. Takeuchi, C.K. Hanson, M.E. Wadsworth, Kinetics and mechanism of the dissolution of thorium oxide in hydrofluoric acid and nitric acid mixtures, J. Inorg. Nucl. Chem. 33 (1971) 1089–1098. [2] M. Akabori, T. Shiratori, Dissolution of ThO2-based oxides in nitric acid solutions at elevated temperatures, J. Nucl. Sci. Technol. 31 (1994) 539–545. [3] S. Chaudhury, M. Keskar, A.V. Patil, K.D.S. Mudher, V. Venugopal, Studies on the dissolution behaviour of ThO2 and (U, Th)O2 by a solid state reaction method, Radiochim. Acta 94 (2006) 357–361. [4] Dissolution of thorium(IV) oxide: To a powdered ThO2 (100 mg, 0.379 mmol, 99.9% Matthey Reagent) 0.5 mL water and 2.5 mL trifluoromethanesulfonic (triflic) acid (98% Fluka) were added. The mixture was heated under reflux in a small round-bottomed flask. During this time the temperature at the bottom of the flask was maintained in the range 170–190 °C. After about 10 min a clear slightly pink liquid phase containing aqueous solution of thorium(IV) triflate was obtained. This method was the subject of Polish and European patent application in 2010 and 2011, respectively. [5] IR data (KBr pellet, cm−1): 3500-3300(vs, vbr) νs(OH), 1626(m) δ(HOH), 1275(sh) νas(SO3), 1250(vs) νs(CF3), 1176(m) νas(CF3), 1048(sh), 1033(s) νs(SO3), 767(vw)
[17]
[18]
σs(CF3), 655(m) σs(SO3), 580(vw) σas(CF3), 521(w) σas(SO3) (the same spectra were registered for both forms of thorium(IV) triflate, see also supplementary material); assignments based on [18]. M. Bouby, I. Billard, J. MacCordick, Complexation of Th(IV) with the siderophore pyoverdine A, J. Alloys Compd. 271–273 (1998) 206–210. M. Walker, Process for the preparation of aryl ketones generating reduced amounts of toxic byproducts, US Patent 6362375 (2002). Crystal data for [Th(CF3SO3)4(H2O)2]n: C4H4F12O14S4Th, FW = 864.35, monoclinic, space group P 21/c, a = 10.7700(2) Å, b = 18.4270(2) Å, c = 10.9038(2) Å, β = 103.643(2)° V= 2102.90(6) Å3, Z = 4, Dc = 2.730 g/cm3, μ = 7.656 mm −1, F(000) = 1608, 18626 reflections collected, 5017 unique (Rint = 0.0444), Data/ restraints/parameters: 5017/1/431, GOF = 1.062, final R indices [I> 2σ(I)]: R1 = 0.0285, wR2 = 0.0639, R indices (all data): R1 = 0.0367, wR2 = 0.0679, largest difference peak and hole: 2.32 and −1.59 (0.96 and 1.35 Å from Th1) e·A-3. The single-crystal X-ray diffraction measurement was carried out at 100(2) K on an Agilent Technologies SuperNova (Dual) Eos CCD diffractometer with MoKα radiation (λ=0.71073 Å). The structure was solved by direct methods and refined with full-matrix least-squares technique using SHELXTL program package. All non-hydrogen atoms were refined anisotropically. The hydrogen atoms were placed in calculated positions and refined as riding atoms with common fixed isotropic thermal factors. Analytical numeric absorption correction was applied using CrysAlisPro program. N. Torapava, I. Persson, L. Eriksson, D. Lundberg, Hydration and hydrolysis of thorium(IV) in aqueous solution and the structures of two crystalline thorium(IV) hydrates, Inorg. Chem. 48 (2009) 11712–11723. C. Brouca-Cabarrecq, J.-C. Trombe, f Element croconates 2. Thorium(IV) and dioxouranium(VI) croconates — synthesis, crystal structure and thermal behaviour, Inorg. Chim. Acta 191 (1992) 241–248. R.W.H. Pohl, J. Wiebke, A. Klein, M. Dolg, N. Maggiarosa, A new 5,5′-bitetrazole thorium(IV) compound: synthesis, crystal structure and quantum chemical investigation, Eur. J. Inorg. Chem. (2009) 2472–2476. R.E. Wilson, S. Skanthakumar, P.C. Burns, L. Soderholm, Angew. Chem. Int. Ed. 46 (2007) 8043–8045. The XPS data for samples obtained from decomposition of greyish-white solid form of thorium(IV) triflate: a) under nitrogen atmosphere (in at.%): O (57.2), Th (25.8), F (9.4), C (6.8), and b) under air atmosphere (in at.%): O (58.9), Th (21.7), C (9.8), S (6.8), F (2.1) (only elements with content above 1 at.% are mentioned). All XPS spectra were recorded on a PHI 5000 Versa Probe spectrometer using monochromatic Al Kα radiation. On the base of TGA curves we have estimated a composition of a greyish-white solid form of thorium(IV) triflate as Th(CF3SO3)4·0.1CF3SO3H·2H2O assuming that the whole amount of the studied compound decomposed to ThO2. (a) N.T. McDevitt, W.L. Baun, Infrared absorption study of metal oxides in the low frequency region (700–240 cm−1), Spectrochim. Acta 20 (1964) 799–808; (b) M. Terada, M. Tsuboi, Infrared-active lattice vibrations in a few fluorite-type crystals, Bull. Chem. Soc. Jpn. 37 (1964) 1080–1081. (a) The International Centre for Diffraction Data (ICDD), Powder Diffraction File database. (b) A. Rhandour, J.-M. Reau, S. Matar, P. Hagenmuller, Influence de l'oxygène sur les propriétés cristallographiques et électriques des materiaux de type tysonite, J. Solid State Chem. 64 (1986) 206–216; (c) T.K. Keenan and L.B. Asprey, Lattice constants of actinide tetrafluorides including berkelium, Inorg. Chem. 8 (1960) 235–238. (d) W.H. Zachariasen, Crystal chemical studies of the 5f-series of elements. XIII. The crystal structure of U2F9 and NaTh2F9, Acta Cryst. 2 (1949) 390–393. (a) N. Yanagihara, S. Nakamura, M. Nakayama, Thermal study of several lanthanide triflates, Polyhedron 17 (1998) 3625–3631; (b) K. Egashira, Y. Yoshimura, H. Kanno, Y. Suzuki, TG-DTA study on the lanthanoid trifluoromethanesulfonate complexes, J. Therm. Anal. Calorim. 71 (2003) 501–508. D.H. Johnston, D.F. Shiver, Vibrational study of the trifluoromethanesulfonate anion: unambiguous assignment of the asymmetric stretching modes, Inorg. Chem. 32 (1993) 1045–1047.