Sc2[Se2O5]3: The First Rare-Earth Metal Oxoselenate(IV) with Exclusively [Se2O5]2− Anions

Greiner, Stefan; Schleid, Thomas

doi:10.3390/cryst8050187

Open AccessArticle

Sc₂[Se₂O₅]₃: The First Rare-Earth Metal Oxoselenate(IV) with Exclusively [Se₂O₅]²⁻ Anions

by

Stefan Greiner

and

Thomas Schleid

^*

Institute for Inorganic Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany

^*

Author to whom correspondence should be addressed.

Crystals 2018, 8(5), 187; https://doi.org/10.3390/cryst8050187

Submission received: 23 March 2018 / Revised: 20 April 2018 / Accepted: 20 April 2018 / Published: 26 April 2018

(This article belongs to the Special Issue Crystal Structures of Compounds Containing Ions Selenite)

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Abstract

:

The scandium oxodiselenate(IV) Sc₂[Se₂O₅]₃ was synthesized via solid-state reactions between scandium sesquioxide (Sc₂O₃) and selenium dioxide (SeO₂) with thallium(I) chloride (TlCl) as fluxing agent in molar ratios of 1:4:2. Evacuated fused silica ampoules were used as reactions vessels for annealing the mixtures for five days at 800 °C. The new scandium compound crystallizes in the triclinic space group P

\bar{1}

with the lattice parameters a = 663.71(5) pm, b = 1024.32(7) pm, c = 1057.49(8) pm, α = 81.034(2)°, β = 87.468(2)°, γ = 89.237(2)° and Z = 2. There are two distinct Sc³⁺ positions, which show six-fold coordination by oxygen atoms as [ScO₆]⁹⁻ octahedra (d(Sc–O) = 205–212 pm). Three different [Se₂O₅]²⁻ anions provide these oxygen atoms with their terminal ligands (O^t). Each of the six selenium(IV) central atoms exhibit a stereochemically active lone pair of electrons, so that all [Se₂O₅]²⁻ anions consist of two ψ¹-tetrahedral [SeO₃]²⁻ subunits (d(Se–O^t) = 164–167 pm, d(Se–O^b) = 176–185 pm, ∢(O–Se–O) = 93–104°) sharing one bridging oxygen atom (O^b) with ∢(Se–O^b–Se) = 121–128°. The vibrational modes of the complex anionic [Se₂O₅]²⁻ entities were characterized via single-crystal Raman spectroscopy.

Keywords:

scandium; lone-pair; oxoselenate; complex anions; Raman spectroscopy; solid-state reactions

1. Introduction

Owing to their potential as materials with an inorganic antenna effect [1] within energy transfer processes for lighting applications, many rare-earth metal(III) oxoselenates(IV) were published with different structural characteristics in the past decades. So even the pure rare-earth metal(III) oxoselenates(IV) with the simple formula RE₂[SeO₃]₃ (≡ RE₂Se₃O₉; RE = Sc, Y, La–Lu) [2,3,4,5,6,7,8,9,10,11,12] show a cornucopia of structure and space-group types. For the smallest rare-earth metal, scandium Sc₂[SeO₃]₃ crystallizes in a hexagonal crystal structure in space group P6₃/m [3]. In contrast, the RE₂[SeO₃]₃-type phases with lanthanum and cerium show an orthorhombic structure in space-group Pnma [2,4]. The next two lanthanides, praseodymium and neodymium, exhibit for their RE₂[SeO₃]₃ compounds the monoclinic crystal system with the space group P2₁/n [2,8]. All further rare-earth metals(III) (RE = Y, Sm–Lu) [6,7,10] adopt the same triclinic crystal structure for their RE₂[SeO₃]₃-type representatives with space-group P

\bar{1}

. Besides this formula type, representatives containing oxygen atoms not bonded to the Se⁴⁺ cations are known with the formula RE₂O[SeO₃]₂ (≡ RE₂Se₂O₇; RE = Y, Sm–Tm) [13,14,15,16]. Most of the compounds crystallize in the tetragonal Tb₂O[SeO₃]₂ structure-type [16], but the newest experimental research shows that monoclinic Sm₃O₂Sm[SeO₃]₄ (≡ Sm₂Se₂O₇) is also accessible [15]. All these compounds exhibit the same basic module, which is responsible for the crystal structure, and these basic modules are oxygen-centered [ORE₄]¹⁰⁺ tetrahedra, which are interconnected in different ways. Furthermore, in the literature is a rare-earth metal(III) oxoselenate(IV) known with two ‘free’ oxygen atoms per formula unit and the composition Sc₂O₂[SeO₃] [17,18]. This formula type RE₂O₂[SeO₃] (≡ RE₂SeO₅) was long postulated from Oppermann et al. [19,20,21,22,23] in various RE₂O₃/SeO₂ systems. Nevertheless, no single crystals were available to confirm this crystal structure, so it was only assumed via powder diffraction methods [19,20,21,22,23]. Only one representative, including rare-earth metals, is known so far in the literature, which exhibits complex anionic [Se₂O₅]²⁻ units. Sm₂[SeO₃][Se₂O₅]₂ (≡ Sm₂Se₅O₁₃) [24] contains only two of these anions, while with the title compound the first rare-earth metal(III) oxoselenate(IV) was accessible with exclusively these sort of anions. The aim of the synthesis was a TlSc[SeO₃]₂, however, which should be structurally similar to the alkali-metal scandium oxoselenates(IV) ASc[SeO₃]₂ (A = Na–Cs) [25] known in the literature. This paper describes the crystal structure of the new title compound Sc₂[Se₂O₅]₃ as well as the vibrational modes of the [Se₂O₅]²⁻ groups via single-crystal Raman measurements.

2. Materials and Methods

For the synthesis of the scandium oxodiselenate(IV) Sc₂[Se₂O₅]₃ a mixture of Sc₂O₃ (ChemPur: 99.9%), SeO₂ (ChemPur: 99.9%) and TlCl (Alfa Aesar: ‘pure’) in a molar ratio of 1:4:2 was used. The target product was thus TlSc[SeO₃]₂ according to the known alkali-metal scandium oxoselenates(IV) ASc[SeO₃]₂ (A = Na–Cs) [25]. The chemicals were stored and handled in a glove box (GS Glove-Box Systems) under an argon atmosphere. The reactants were filled into glassy fused silica ampoules, which were evacuated to 10⁻³ mbar and torch sealed. Afterwards, the reaction vessels were heated up over 8 h to 800 °C and tempered for five days at this temperature. The furnace was cooled down to 500 °C within 99 h, and held at this temperature for another 2 h, before it was completely cooled down within 4 h to room temperature. The crude product was checked for its water- and air-stability. Afterwards it was washed with demineralized water to remove most of the fluxing agents (SeO₂ and TlCl). Some colorless, plate-like crystals were selected and characterized via X-ray structure analysis. For this purpose, the crystals were measured at room temperature on a κ-CCD X-ray diffractometer (Bruker Nonius, Karlsruhe, Germany) with graphite-monochromatized Mo-Kα radiation (λ = 71.07 pm). A numerical absorption correction was carried out with the program HABITUS [26], but the structure solution and refinement was performed with the program SHELX-97 [27,28]. In Table 1 the crystallographic data of Sc₂[Se₂O₅]₃ are summarized, while Table 2 contains the atomic positions and their equivalent isotropic displacement coefficients. The interatomic distances and bond angles are shown in Table 3.

The reflections in the X-ray powder pattern (Figure 1) exhibit a low intensity due to the poor crystallinity of the product, therefore a good evaluation and characterization was not possible (Figure 1). However, scandium oxoselenate(IV) Sc₂[SeO₃]₃ and some residual thallium(I) chloride TlCl could be identified as by-products. In addition, the powder pattern shows reflections of another side phase, which could not be determined so far. Hence, a successful synthesis of the phase pure title compound Sc₂[Se₂O₅]₃ was not successful yet.

The single-crystal Raman measurements were operated on a XploRa device (Horiba, Bensheim, Germany) from 200–1000 cm⁻¹ to detect the vibrational modes of the complex anionic [Se₂O₅]²⁻ anions. Further details of the crystal structure investigations can be obtained at the Fachinfomrationszentrum Karlsruhe, 76334 Eggenstein-Leopoldshafen, Germany (Fax: +49-7247-808-666; E-Mail: crysdata@fiz-karlsruhe.de, http://www.fiz-karlsruhe.de/request for deposited data.html) for the depository number CSD-433355 of Sc₂[Se₂O₅]₃.

3. Results and Discussion

The new scandium oxodiselenate(IV) Sc₂[Se₂O₅]₃ (≡ Sc₂Se₆O₁₅) crystallizes in the triclinic space group P

\bar{1}

(no. 2) with the lattice parameters a = 663.71(5) pm, b = 1024.32(7) pm, c = 1057.49(8) pm, α = 81.034(2)°, β = 87.468(2)°, γ = 89.237(2)°, and Z = 2 (Table 1). In the crystal structure, two distinct Sc³⁺ cations exist (Table 2). Both of them are six-fold coordinated by oxygen atoms as [ScO₆]⁹⁻ octahedra, which belong to six terminally attached [Se₂O₅]²⁻ units (Figure 2). The Sc³⁺–O²⁻ distances range in the area of 204 to 212 pm (Table 3). These correlate well with them known from the scandium oxoselenate(IV) Sc₂[SeO₃]₃ (d = 201–220 pm) [3].

Moreover, three different complex anionic [Se₂O₅]²⁻ groups occur in the crystal structure (Figure 3), showing different dihedral angles between the two (O,O,O)-faces ((O1,O2,O3)–(O3,O4,O5) = 121.2°; (O6,O7,O8)–(O8,O9,O10) = 146.0°; (O11,O12,O13)–(O13,O14,O15) = 152.2°). The Se⁴⁺–O²⁻ distances are located in an interval from 164 to 167 pm (Table 3), this is slightly smaller than those in downeyite-type SeO₂ (d = 171–173 pm) [29]. In contrast, the Se⁴⁺–(O^b)²⁻ distances are significantly longer with 177 to 185 pm. Similar distances were found in the first known lanthanoid(III) oxoselenate(IV) with [Se₂O₅]²⁻ units, Sm₂[SeO₃][Se₂O₅]₂ (≡ Sm₂Se₅O₁₃, d = 164–184 pm) [24] namely. The [ScO₆]⁹⁻ octahedra are interconnected via the terminally grafting [Se₂O₅]²⁻ units resulting in the three-dimensional network of Sc₂[Se₂O₅]₃ (Figure 4). The displacements of the Se⁴⁺ cations from their triangular (O,O,O)-plane are for all three complex anionic [Se₂O₅]²⁻ anions very much alike. These displacements range from 77.3 pm (Se1), 78.3 pm (Se3), 79.4 pm (Se6), 79.5 pm (Se5), 79.7 pm (Se2), to 82.0 pm (Se4). Also the Se–O^b–Se angles are located in a small area with (Se1)–(O3)^b–(Se2) = 121.3°, (Se3)–(O8)^b–(Se4) = 126.3°, and (Se5)–(O13)^b–(Se6) = 127.5°.

Raman-spectroscopic measurements of Sc₂[Se₂O₅]₃ single crystals show typically modes, known from free [SeO₃]²⁻ units with ψ¹-tetrahedral shape and ideal C_3v symmetry. These modes belong to two symmetric vibrations with A₁ at 810 and 425 cm⁻¹ and E at 740 and 375 cm⁻¹ according to Siebert [30]. By the influence of the crystal field these bands of the [SeO₃]²⁻ anions split up into wide areas. The symmetric stretching modes are located in the range of 890–790 cm⁻¹ (ν_s) and the anti-symmetric stretching modes occur between 760 and 660 cm⁻¹ (ν_as). According to these, also the bending modes have an expanded area with the symmetric bending mode between 510 and 420 cm⁻¹ (δ_s) and anti-symmetric bending mode from 410 up to 330 cm⁻¹ [30]. The complex anionic oxodiselenate(IV) units generate one more stretching mode resulted from the slightly longer Se⁴⁺–(O^b)²⁻ bond by about 10 to 15 pm expanded. This mode is located between 650 and 550 cm⁻¹ [12] and seems to be specific for [Se₂O₅]²⁻ anions (ν_SeOB). In the Raman spectrum three signals can be detected in this area with ν = 578, 606 and 632 cm⁻¹. For the symmetric stretching mode (ν_s) two signals appear at 901 and 934 cm⁻¹ and for the anti-symmetric stretching mode (ν_as) three at 739, 800, and 811 cm⁻¹. In the area of the symmetric bending mode ν = 420–550 cm⁻¹ (δ_s) four signals can be found at 435, 469, 523, and 539 cm⁻¹. At smaller wavenumbers between 208 and 387 cm⁻¹, the anti-symmetric bending modes as well as lattices vibrations are located. Seven signals at 208, 235, 274, 292, 322, 347, and 387 cm⁻¹ become obvious in these areas (Figure 5). For the characterization of these modes modern articles were used as references [11,18,31,32,33].

4. Conclusions

Unlike yttrium, its heavier congener in group III of the periodic table of the elements, scandium hardly forms compounds suitable as hosts for doping with appropriate lanthanoid(III) cations (e.g., Eu³⁺ or Tb³⁺) for luminescence materials. Its small ionic radius (r:(Sc³⁺) = 74.5 pm for C.N. = 6 [34]) and its preference for octahedral coordination figures explain this finding plausibly, whereas yttrium (r:(Y³⁺) = 101.9 pm for C.N. = 8 [34]) ranges within the heavy lanthanoid compartment (Dy³⁺, Ho³⁺, or Er³⁺) under these circumstances, without being a 4f element. So even with nice [SeO₃]²⁻ pyramids as building blocks with a lone-pair of electron at the Se⁴⁺ cations, scandium(III) oxoselenate(IV) derivatives are unable to host Ln³⁺ cations, as long as they contain only six-fold coordinated Sc³⁺ cations, e.g., Sc₂[SeO₃]₃ [3], Sc₂O₂[SeO₃] [17,18] and our new example Sc₂[Se₂O₅]₃. However this changes, whenever the Sc³⁺ cations reside in coordination polyhedra with higher coordination numbers. In the case of ScF[SeO₃] [17,18,35] and ScCl[SeO₃] [17,36] with seven-fold coordinated Sc³⁺ cations in pentagonal bipyramids, Eu³⁺ cations can replace these partially (1–5%), which leads to red luminescent materials in the case of ScF[SeO₃]:Eu³⁺ [17]. The tight [ScO₅F₂]⁹⁻ polyhedra provoke a slight red-shift of the Eu³⁺-centered luminescence, however, as compared to the YF[SeO₃]:Eu³⁺ example [10] with Eu³⁺ in the eight-fold coordination of [YO₆F₂]¹¹⁻ polyhedra.

Supporting Materials

The CIF of the title compound can be downloaded directly with the publication, containing all crystallographic data.

Author Contributions

Stefan Greiner and Thomas Schleid conceived and designed the experiments; Stefan Greiner performed the experiments; Stefan Greiner and Thomas Schleid analyzed the data; Thomas Schleid contributed reagents/materials/analysis tools; Stefan Greiner wrote the paper and Thomas Schleid polished it.

Acknowledgments

We thank Sabine Strobel for the single-crystal X-ray diffraction measurement. Additionally, we are grateful to Adrian H. Geyer for the single-crystal Raman analysis. Finally, we acknowledge the considerable financial support by the State of Baden-Württemberg (Stuttgart).

Conflicts of Interest

The authors declare no conflict of interest.

References

Blasse, G.; Grabmaier, B.C. Luminescent Materials; Springer: Berlin/Heidelberg, Germany, 1994. [Google Scholar]
Wontcheu, J.; Schleid, T. Ce₂[SeO₃]₃ and Pr₂[SeO₃]₃: Non-Isostructural Oxoselenates(IV) of the Light Lanthanoids. Z. Anorg. Allg. Chem. 2006, 632, 645–654. [Google Scholar] [CrossRef]
Wontcheu, J.; Schleid, T. Sc₂Se₃O₉: Scandium(III) Oxoselenate(IV) According to Sc₂[SeO₃]₃ with a Hexagonal “Lone-Pair” Channel Structure. Z. Anorg. Allg. Chem. 2003, 629, 1463–1465. [Google Scholar] [CrossRef]
Harrison, W.T.A. Lanthanum selenite, La₂(SeO₃)₃. Acta Crystallogr. 2000, 56, 627–628. [Google Scholar]
Wickleder, M.S. Wasserfreie Selenite des Lanthans: Synthese und Kristallstruktur von La₂(SeO₃)₃ und LaFSeO₃. Z. Anorg. Allg. Chem. 2000, 626, 547–551. [Google Scholar] [CrossRef]
Krügermann, I.; Wickleder, M.S. Syntheses and Crystal Structures of Er₂(SeO₃)₃ and Dy₃(SeO₃)₄F. J. Solid State Chem. 2002, 167, 113–118. [Google Scholar] [CrossRef]
Krügermann, I.; Wickleder, M.S.; Wontcheu, J.; Schleid, Th. The Unique Crystal Structure of the Triclinic Samarium(III) Oxoselenate(IV) Sm₂[SeO₃]₃. Z. Anorg. Allg. Chem. 2006, 632, 901–904. [Google Scholar] [CrossRef]
Krügermann, I.; Wickleder, M.S. Kristallstruktur und Phasenumwandlung von Nd₂(SeO₃)₃. Z. Anorg. Allg. Chem. 2002, 628, 2197. [Google Scholar] [CrossRef]
Krügermann, I. Oxoselenate(IV/VI) der Selten-Erd-Elemente und ihre Derivate. Ph.D. Thesis, Universität Köln, Cologne, Germany, 2002. [Google Scholar]
Wontcheu, J. Oxoselenates(IV) of the Trivalent Rare-Earth Elements and Some Derivatives. Ph.D. Thesis, Universität Stuttgart, Stuttgart, Germany, 2004. [Google Scholar]
Chou, S.-C. Rare-Earth Metal(III) Oxoselenates(IV) and Oxotellurates(IV) and Investigation of Their Luminescent Properties. Ph.D. Thesis, Universität Stuttgart, Stuttgart, Germany, 2015. [Google Scholar]
Wickleder, M.S. Handbook on the Physics and Chemistry of Rare Earths; Gschneidner, K.A., Jr., Bünzli, J.-C.G., Pecharsky, V.K., Eds.; Elsevier Scinece Publishers: New York, NY, USA, 2005; Volume 35. [Google Scholar]
Greiner, S. Untersuchungen zum Antennen-Effekt bei lanthanoidischen Leuchtstoffen auf Oxoselenat(IV)-Basis. Bachelor Thesis, Universität Stuttgart, Stuttgart, Germany, 2013. [Google Scholar]
Wontcheu, J.; Zitzer, S.; Schleid, Th. Die Lanthanoid(III)-Oxid-Oxoselenate(IV) Ln₂O[SeO₃]₂ (Ln = Sm − Tm). Z. Naturforsch. 2016, 71b, 1279–1285. [Google Scholar] [CrossRef]
Zitzer, S.; Su, S.-H.; Greiner, S.; Schleid, Th. Sm₂Se₂O₇ and Sm₃O₂Cl[SeO₃]₂: A New Monoclinic Modification of Samarium(III) Oxide Oxoselenate(IV) and a Samarium(III) Oxide Chloride Oxoselenate(IV) Both Containing Oxygen-Centered Samarium Tetrahedra. Z. Anorg. Allg. Chem. 2018, in press. [Google Scholar]
Wontcheu, J.; Schleid, Th. Tb₂Se₂O₇: Terbium(III) Oxide Oxoselenate(IV) according to Tb₂O[SeO₃]₂ with a “Lone-Pair” Channel Structure. Z. Anorg. Allg. Chem. 2002, 628, 1941–1945. [Google Scholar] [CrossRef]
Greiner, S. Scandium(III)-Oxoselenate(IV) als kompakte Wirtsgitter für Lanthanoid-Dotierungen. Master’s Thesis, Universität Stuttgart, Stuttgart, Germany, 2015. [Google Scholar]
Greiner, S.; Chou, S.-C.; Schleid, Th. Two anionically derivatized scandium oxoselenates(IV): ScF[SeO₃] and Sc₂O₂[SeO₃]. J. Solid State Chem. 2017, 246, 160–166. [Google Scholar] [CrossRef]
Zhang-Preße, M.; Oppermann, H. Thermochemical Investigation of RE₂O₃–SeO₂ Systems, III. Yttrium selenium oxides in the pseudo-binary system. J. Therm. Anal. Calorim. 2002, 69, 301–316. [Google Scholar] [CrossRef]
Zhang-Preße, M.; Oppermann, H. Thermochemische Untersuchungen zu den Systemen SE₂O₃–SeO₂, IV. Lösungskalorimetrie der SE₂Se_xO_3+2x-Phasen (SE = Nd, Sm, Y). Z. Naturforsch 2002, 57b, 661–667. [Google Scholar]
Oppermann, H.; Zhang-Preße, M.; Schmidt, P. Thermochemische Untersuchungen zu den Systemen SE₂O₃–SeO₂, V. Ytterbiumselenoxide auf dem Schnitt Yb₂O₃–SeO₂. Z. Naturforsch. 2002, 57b, 868–876. [Google Scholar]
Oppermann, H.; Zhang-Preße, M.; Weck, S.; Liebig, S. Thermochemische Untersuchungen zu den Systemen SE₂O₃/SeO₂, I. Neodymselenoxide auf dem Schnitt Nd₂O₃–SeO₂. Z. Anorg. Allg. Chem. 2002, 628, 81–90. [Google Scholar] [CrossRef]
Oppermann, H.; Zhang-Preße, M. Thermochemische Untersuchungen zu den Systemen SE₂O₃–SeO₂, II. Samariumselenoxide auf dem Schnitt Sm₂O₃–SeO₂. Z. Naturforsch 2001, 56b, 917–926. [Google Scholar]
Wickleder, M.S. Sm₂Se₅O₁₃: A Selenite–Diselenite according to Sm₂(SeO₃)(Se₂O₅)₂. Z. Anorg. Allg. Chem. 2006, 632, 2377–2379. [Google Scholar] [CrossRef]
Song, S.Y.; Ok, K.M. Modulation of Framework and Centricity: Cation Size Effect in New Quaternary Selenites, ASc(SeO₃)₂ (A = Na, K, Rb, and Cs). Inorg. Chem. 2015, 54, 5032–5038. [Google Scholar] [CrossRef] [PubMed]
Herrendorf, W.; Bärnighausen, H. HABITUS: Programm zur Optimierung der Kristallgestalt für die Numerische Absorptionskorrektur als Version X-SHAPE, version 1.06; Universität Karlsruhe 1993, Universität Gießen 1996; Fa. Stoe: Darmstadt, Germany, 1999. [Google Scholar]
Sheldrick, G.M. SHELX-97: Program Suite for the Solution and Refinement of Crystal Structures; Universität Göttingen: Göttingen, Germany, 1997. [Google Scholar]
Sheldrick, G.M. A short history of SHELX. Acta Crystallogr. 2008, 64, 112–122. [Google Scholar] [CrossRef] [PubMed]
McCullough, J.D. The Crystal Structure of Selenium Dioxide. J. Am. Chem. Soc. 1937, 59, 789–794. [Google Scholar] [CrossRef]
Siebert, H. Anwendung der Schwinungsspektroskopie in der Anorganischen Chemie; Springer: Berlin/Heidelberg, Germany; New York, NY, USA, 1966. [Google Scholar]
Zitzer, S. Selten-Erd-Metall(III)-Oxoselenate(IV) und -Oxotellurate(IV): Synthese, Kristallstrukturaufklärung und fluoreszenzspektroskopische Untersuchungen ausgewählter Leuchtstoffe. Ph.D. Thesis, Universität Stuttgart, Stuttgart, Germany, 2011. [Google Scholar]
Ok, K.M.; Halasyamani, P.S. New Selenites: Syntheses, Structures, and Characterization of Centrosymmetric Al₂(Se₂O₅)₃ and Ga₂(Se₂O₅)₃ and Non-centrosymmetric In₂(Se₂O₅)₃. Chem. Mater. 2002, 14, 2360–2364. [Google Scholar] [CrossRef]
Verma, V.P. A review of synthetic, thermoanalytical, IR, Raman and X-ray studies on metal selenites. Thermochim. Acta 1999, 327, 63–102. [Google Scholar] [CrossRef]
Shannon, R.D. Revised Effective Ionic Radii and Systematic Studies of Interatomic Distances in Halides and Chalcogenides. Acta Crystallogr. 1976, 32, 751–767. [Google Scholar] [CrossRef]
Chou, S.-C.; Greiner, S.; Magdysyuk, O.V.; Dinnebier, R.E.; Schleid, Th. Theoretical and Experimental Analysis of Structural Phase Transitions for ScF[SeO₃] and YF[SeO₃]. Z. Anorg. Allg. Chem. 2014, 640, 3203–3211. [Google Scholar] [CrossRef]
Greiner, S.; Schleid, T.H. ScCl[SeO₃]: The Chloride Oxoselenate(IV) of the Smallest Rare-Earth Metal. Z. Anorg. Allg. Chem. 2016, 642, 1076. [Google Scholar]

Figure 1. Measured powder pattern of the title compound (black) with the reference of Sc₂[Se₂O₅]₃ (red), Sc₂[SeO₃]₃ (green), and TlCl (blue) from single crystal data.

Figure 2. Coordination sphere of the two crystallographically distinct Sc³⁺, which are six-fold coordinated by oxygen atoms as [ScO₆]⁹⁻ octahedra ((top left) and (bottom left)). The oxygen atoms themselves belong to six terminally attached [Se₂O₅]²⁻ anions. Symmetry related atoms are shown with an ^a(x, y, z) or ^b(−x, −y, −z) and a thermal ellipsoid representation with probability factor of 95% (left).

Figure 3. Configuration of the three different [Se₂O₅]²⁻ groups in the crystal structure of triclinic Sc₂[Se₂O₅]₃. These consist of two via vertex interconnected ψ¹-tetrahedral [SeO₃]²⁻ subunits with different tilting angles between their two (O,O,O)-faces. In addition, the cationic coordination sphere of the [Se₂O₅]²⁻ anions is shown (thermal ellipsoid representation with probability factor of 95%). Note that none of the bridging oxygen atoms (O3, O8, and O13) has a coordinative contacts to the Sc³⁺ cations.

Figure 4. All [ScO₆]⁹⁻ octahedra are interconnected by terminally attached [Se₂O₅]²⁻ anions to form the three-dimensional network of triclinic Sc₂[Se₂O₅]₃.

Figure 5. Single-crystal Raman spectrum of Sc₂[Se₂O₅]₃ in the area from 200 to 1000 cm⁻¹. The different stretching and bending modes of the complex anionic [Se₂O₅]²⁻ units are shown.

Table 1. Crystallographic data of Sc₂[Se₂O₅]₃ and their determination.

Empirical Formula	Sc₂[Se₂O₅]₃ (≡ Sc₂Se₆O₁₅)
Crystal system	triclinic
Space group	P $\bar{1}$ (no. 2)
Lattice parameters
a/pm	663.71(5)
b/pm	1024.32(7)
c/pm	1057.49(8)
α/deg	81.034(2)
β/deg	87.468(2)
γ/deg	89.237(2)
Number of formula units (Z)	2
Calculated density (D_x in g/cm³)	3.762
Molar volume (V_m in cm³/mol)	188.58(9)
Diffractometer	κ-CCD (Bruker Nonius)
Wavelength (λ in pm)	71.07 (Mo Kα)
Index range (±h_max, ±k_max, ±l_max)	8/13/13
Number of e⁻ per unit cell (F(000))	732
Absorption coefficient (μ in mm⁻¹)	16.426
Number of collected vs. unique reflections	31217/3256
Data-set residuals (R_int/R_σ)	0.084/0.036
Structure residuals (R₁/wR₂)	0.034/0.074
Goodness of fit (GooF)	1.058
Extinction coefficient (g)	0.0101(5)
Residual electron density (max./min. in e⁻ 10⁻⁶ pm⁻³)	1.318/−1.267
CSD-number	433,355

Table 2. Atomic coordinates and equivalent isotropic displacement coefficients (U_eq/pm²) for Sc₂[Se₂O₅]₃ (all atoms occupy the general 2i site)

Atom	x/a	y/b	z/c	U_eq¹
Sc1	0.16448(9)	0.58715(7)	0.26677(7)	145(2)
Sc2	0.31102(9)	0.06071(7)	0.28974(7)	143(2)
Se1	0.22321(5)	0.77750(4)	0.51356(4)	173(1)
Se2	0.31368(5)	0.30185(4)	0.49159(4)	156(1)
Se3	0.14680(5)	0.33785(4)	0.08075(4)	197(1)
Se4	0.34062(5)	0.46713(4)	0.80898(4)	189(1)
Se5	0.20134(5)	0.01376(4)	0.77299(4)	171(1)
Se6	0.32216(5)	0.85034(4)	0.04488(4)	173(1)
O1	0.3565(4)	0.8834(3)	0.4083(3)	257(6)
O2	0.1123(4)	0.6849(3)	0.4203(3)	241(6)
O3	0.4252(4)	0.6720(3)	0.5744(3)	229(6)
O4	0.2120(4)	0.4093(3)	0.3801(3)	245(6)
O5	0.2599(4)	0.1567(3)	0.4489(3)	210(6)
O6	0.3013(4)	0.2435(3)	0.1727(3)	288(7)
O7	0.1988(4)	0.4927(3)	0.1010(3)	289(7)
O8	0.2873(4)	0.3302(3)	0.9362(3)	354(8)
O9	0.1421(4)	0.4542(3)	0.7240(3)	308(7)
O10	0.4805(4)	0.6157(3)	0.2594(3)	241(6)
O11	0.0055(4)	0.0288(3)	0.2913(3)	289(7)
O12	0.3733(4)	0.9148(3)	0.7186(3)	227(6)
O13	0.1454(4)	0.9259(3)	0.9300(3)	346(8)
O14	0.3719(4)	0.9735(3)	0.1228(3)	288(7)
O15	0.1445(4)	0.7649(3)	0.1370(3)	229(6)

¹ defined as temperature factor according to: exp[−2π²(U₁₁h²a*² + U₂₂k²b*² + U₃₃l²c*² + 2U₁₃hla*c* + 2U₁₂hka*b* + 2U₂₃hlb*c*)].

Table 3. Selected interatomic distances (d/pm) and angles (∢/°) in the crystal structure of Sc₂[Se₂O₅]₃.

Sc1–O4	204.7(3)	Sc2–O11	205.7(3)
Sc1–O2	205.1(3)	Sc1–O1	206.7(3)
Sc1–O9	207.9(3)	Sc1–O6	207.9(3)
Sc1–O15	210.9(3)	Sc1–O5	209.1(3)
Sc1–O10	211.8(3)	Sc1–O12	211.0(3)
Sc1–O7	213.3(3)	Sc1–O14	212.1(3)
Se1–O1	166.1(3)	Se2–O4	164.4(3)
Se1–O2	167.0(3)	Se1–O5	166.7(3)
Se1–O3	178.9(3)	Se1–O3	184.6(3)
Se3–O6	164.3(3)	Se4–O9	164.5(3)
Se1–O7	167.6(3)	Se1–O10	165.6(3)
Se1–O8	176.7(3)	Se1–O8	181.3(3)
Se5–O11	165.2(3)	Se6–O14	165.5(3)
Se1–O12	166.0(3)	Se1–O15	166.3(6)
Se1–O13	178.7(3)	Se1–O13	180.6(3)
O1–Se1–O3	098.52(13)	O3–Se2–O4	095.05(13)
O2–Se1–O3	101.80(14)	O3–Se2–O5	101.58(14)
O1–Se1–O2	102.67(14)	O4–Se2–O5	103.23(14)
O6–Se3–O8	095.50(15)	O8–Se4–O10	093.04(15)
O7–Se3–O8	099.83(15)	O8–Se4–O9	098.24(16)
O6–Se3–O7	105.18(15)	O9–Se4–O10	104.03(15)
O11–Se5–O13	096.13(15)	O13–Se6–O15	093.44(13)
O12–Se5–O13	100.96(15)	O13–Se6–O14	102.13(15)
O11–Se5–O12	102.11(14)	O14–Se6–O15	103.96(15)
Se1–O3–Se2	121.32(14)	Se3–O8–Se4	126.31(18)
Se5–O13–Se6	127.48(17)

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Greiner, S.; Schleid, T. Sc₂[Se₂O₅]₃: The First Rare-Earth Metal Oxoselenate(IV) with Exclusively [Se₂O₅]²⁻ Anions. Crystals 2018, 8, 187. https://doi.org/10.3390/cryst8050187

AMA Style

Greiner S, Schleid T. Sc₂[Se₂O₅]₃: The First Rare-Earth Metal Oxoselenate(IV) with Exclusively [Se₂O₅]²⁻ Anions. Crystals. 2018; 8(5):187. https://doi.org/10.3390/cryst8050187

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Greiner, Stefan, and Thomas Schleid. 2018. "Sc₂[Se₂O₅]₃: The First Rare-Earth Metal Oxoselenate(IV) with Exclusively [Se₂O₅]²⁻ Anions" Crystals 8, no. 5: 187. https://doi.org/10.3390/cryst8050187

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Greiner, S., & Schleid, T. (2018). Sc₂[Se₂O₅]₃: The First Rare-Earth Metal Oxoselenate(IV) with Exclusively [Se₂O₅]²⁻ Anions. Crystals, 8(5), 187. https://doi.org/10.3390/cryst8050187

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Sc₂[Se₂O₅]₃: The First Rare-Earth Metal Oxoselenate(IV) with Exclusively [Se₂O₅]²⁻ Anions

Abstract

1. Introduction

2. Materials and Methods

3. Results and Discussion

4. Conclusions

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