<ul><li><p>Kurze Mitteilungen</p><p>RbAu(SeO4)2: First Structure Determination of a Ternary Gold Selenate</p><p>Oliver Bchner and Mathias S. Wickleder*</p><p>Kln, Institut fr Anorganische Chemie der Universitt</p><p>Received May 4th, 2004.</p><p>Abstract. Yellow single crystals of RbAu(SeO4)2 were obtainedupon evaporation of a solution prepared from the reaction of ele-mental gold and Rb2CO3 with conc. selenic acid. In the crystalstructure (monoclinic, C2/m, Z 2, a 1078.7(4), b 522.7(1),c 739.3(2) pm, 116.45(2)) Au3 is in square planar coordi-nation of oxygen atoms which belong to four SeO42 ions. Accord-</p><p>The oxidation of elemental gold with concentrated selenic acid iswell known for a long time [1]. Formerly, Au2(SeO4)3 was assumedto be the reaction product and this substance has been shown tobe useful in glass coloring processes [2, 3]. However, roughly twentyyears ago it has been shown that in fact selenites form during thedissolution of elemental gold in selenic acid which have, dependingon the specific conditions, the different compositions Au2(SeO3)2Oand Au2(SeO3)2(Se2O5) [4]. Recently we were able to prepare andto characterize the non-centrosymmetric selenite-selenate Au2(SeO3)2-(SeO4) which was the first selenate of gold, although it containsSeO32 ions additionally [5]. The first reliable report on ternarygold selenates was given by Donova and Siftar [6], who preparedcompounds of the composition MAu(SeO4)2 (M H, K-Cs). Un-fortunately the latter have not been characterized structurally. Werecently showed that in the structure of the respective ternary sul-fates MAu(SO4)2 (M Na-Rb) square planar [AuO4] units arelinked to chains according 1[Au(SO4)4/2] while for CsAu(SO4)2 aconnection of these units to layers was observed [7, 8]. We nowstarted to investigate also the selenates structurally and we herepresent the crystal structure of the first ternary gold selenate whichis surprisingly not isotypic with one of the sulfates.</p><p>Experimental</p><p>Evaporation of a solution which had been obtained by dissolving200 mg elemental gold (gussa, 99.99 %) and 117 mg Rb2CO3(Merck, p.a.) in conc. H2SeO4 led to a yellow powder which con-tained several yellow single crystals RbAu(SeO4)2. Concentratedselenic acid has been prepared in a first step from SeO2 and H2O2according to the route described in [9]. RbAu(SeO4)2 is very hygro-scopic and must be handled in a glove box. Several single crystalswere mounted in glass capillaries (d 0,1 mm). According toorientation images on an image plate diffractometer (STOE IPDSII) they all showed the same monoclinic unit cell. For the bestspecimen intensity data were collected using the same dif-</p><p>* Priv.-Doz. Dr. M. S. WicklederInstitut fr Anorganische ChemieUniversitt zu KlnGreinstrae 6D-50939 KlnFax: 0221 470 5083E-Mail: [email protected]</p><p>Z. Anorg. Allg. Chem. 2004, 630, 15391540 DOI: 10.1002/zaac.200400141 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 1539</p><p>ing to 1[Au(SeO4)4/2] anionic chains are formed which are connec-ted by the Rb ions. The latter are surrounded by two chelatingand six monodentate selenate groups leading to a CN of 10.</p><p>Keywords: Gold; Selenates; Rubidium; Crystal Structure</p><p>Table 1 RbAu(SeO4)2: Lattice parameters, atomic coordinates,Wyckoff notation, equivalent isotropic displacement parameters,and selected distances (pm) and angles ().</p><p>monoclinic, C2/m, Z 2, a 1078.7(4), b 522.7(1), c 739.3(2) pm, 116.45(2)</p><p>Atoma) x/a y/b z/c Ueq101/pm2</p><p>Au 2a 0 0 0 21.8(4)Se 4i 0.1995(2) 1/2 0.1579(3) 17.0(5)O1 4i 0.176(1) 1/2 0.926(2) 24(3)O2 8j 0.117(1) 0.253(2) 0.210(1) 25(2)O3 4i 0.354(1) 1/2 0.330(2) 30(3)Rb 2d 0 1/2 1/2 30.4(7)</p><p>Au-O2 (4x) 199.9(9) O2-Au-O2 (2x) 180(2x) 82.8(5)</p><p>Rb-O1 (2x) 286.1(14) (2x) 97.2(5)-O3 (4x) 302.2(7)-O2 (4x) 320.3(9) O3-Se-O1 117.8(8)</p><p>O3-Se-O2 (2x) 106.7(5)Se-O1 161.7(14) O1-Se-O2 (2x) 112.7(7)</p><p>-O2 (2x) 170.9(9) O2-Se-O2 98.2(6)-O3 158.3(14)</p><p>Ueq1/3[U221/sin2(U11U332U13cos)]</p><p>fractometer. The structure solution and refinement [10] led to thecrystallographic data given in Table 1.</p><p>Results and Discussion</p><p>RbAu(SeO4)2 crystallizes monoclinically with the space group C2/mand is not isotypic with one of the respective sulfates known so far[7, 8]. However, the main structural feature of RbAu(SeO4)2,[AuO4] units linked by tetrahedral anions to infinite chains 1[Au-(SeO4)4/2], is almost the same as found for MAu(SO4)2 (M Na-Rb) (Fig. 1). The gold ion within the square planar [AuO4] unit isis located on a special site (2a) of the space group C2/m and hasfour identical distances of 199.9 pm to the surrounding oxygenatoms (O2). The angles O2-Au-O2 show significant deviations from90 leading to the point group 2/m for the [AuO4] polyhedron. Inall of the structurally similar sulfates the perspective point symmetrywas only 1 although the distances Au-O and the angles O-Au-Oare pretty much in the same range as observed for RbAu(SeO4)2(Table 2). The selenate ions which connect the gold ions exhibit msymmetry according to the site 4i of the selenium atom. The dis-tances Se-O within the tetrahedron are remarkable different. Those</p></li><li><p>O. Bchner, M. S. Wickleder</p><p>Fig. 1 Anionic chains 1[Au(SeO4)4/2] in the crystal structure ofRbAu(SeO4)2. The chains are oriented along the [010] direction(atom labeling according to Table 1).</p><p>Table 2 Comparison of the sulfates MAu(SO4)2 (M Na-Rb)with RbAu(SeO4)2.</p><p>compound spac [AuO4] distances angles/ coordinationgroup symmetry Au-O/pm O-Au-O number of M</p><p>NaAu(SO4)2 P21/n 1 199.9(7) 84.5(3) (2x) 6(2x) 95.5(3) (2x)200.6(7)(2x)</p><p>KAu(SO4)2 C2/c 1 198.0(6) 88.4(2) (2x) 10(2x) 91.6(2) (2x)199.0(5)(2x)</p><p>RbAu(SO4)2 P1 1 198.8(7) 86.0(4) (2x) 12(2x) 94.0(4) (2x)198.1(9)(2x)</p><p>RbAu(SeO4)2 C2/m 2/m 199.9(9) 82.8(5) (2x) 10(4x) 97.2(5) (2x)</p><p>oxygen atoms which are part of the [AuO4] units (O2) show bondlenghts of 170.9 pm (2x) while the remainig two oxygen atoms arefound at a distance of 161.7 (O1) and 158.3 pm (O3), respectively.In the crystal structure the chains [Au(SeO4)4/2] are oriented alongthe [010] direction and separated by the Rb ions (Fig. 2). Thelatter are surrounded by two chelating and six monodentate selen-ate ions leading to a coordination number of ten. Two short dis-tances Rb-O of 286.1 pm are found, the remaining bond lengths</p><p> 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim zaac.wiley-vch.de Z. Anorg. Allg. Chem. 2004, 630, 153915401540</p><p>Fig. 2 Perspective view of the crystal structure of RbAu(SeO4)2along [010]. The chains shown in Fig. 1 are connected by Rb ionsin tenfold coordination of oxygen atoms.</p><p>are 302.2 (4x) and 320.3 (4x) pm, respectively. The observed Rb</p><p>coordination is also different from the findings for RbAu(SO4)2where the coordination number of Rb is 12.</p><p>We are indebted to Prof. Dr. G. Meyer for generous support. Fur-thermore we thank the Fonds der Chemischen Industrie, Frankfurtam Main, for a stipend (O.B.).</p><p>[1] E. Mitscherlich, Poggendorff Ann. 1827, 9, 623.[2] V. Lenher, J. Am. Chem. Soc. 1902, 24, 354.[3] W. E. Coldwell, L. P. Eddy, J. Am. Chem. Soc. 1949, 71, 2247.[4] P. G. Jones, G. M. Sheldrick, E. Schwarzmann, A. Vielmder,</p><p>Z. Naturforsch. 1983, 38b, 10; P. G. Jones, E. Schwarzmann,G. M. Sheldrick, H. Timpe, Z. Naturforsch. 1981, 36b, 1050.</p><p>[5] M. S. Wickleder, O. Bchner, C. Wickleder, Sh. El Sheik, G.Brunklaus, H. Eckert, Inorg. Chem., in press.</p><p>[6] I. Donova, J. Siftar, Thermochim. Acta 1994, 244, 131.[7] M. S. Wickleder, O. Bchner Z. Naturforsch. 2001, 56b, 1340.[8] M. S. Wickleder, K. Esser, Z. Anorg. Allg. Chem. 2002, 628,</p><p>911.[9] G. Brauer, Handbuch der prparativen anorganischen Chemie,</p><p>F. Enke, Stuttgart 1975.[10] The reflection intensities of a single crystal (0.2 x 0.1 x</p><p>0.1 mm) were measured with an IP diffractometer (IPDS II,Stoe & Cie) at 293 K. Data aquisition: Mo-K-radiation(graphite monochromator, 71,07 pm), max 28, 0-180 (2 runs at 90 and 180), 2, 180 images,exposure time: 5 min, detector distance: 100 mm, 2442 mea-sured reflections, 250 unique reflections (Rint 0.0649);Structure solution and refinement: programs SHELXS-86 andSHELXL-93 (G. M. Sheldrick, Gttingen 1986/93), scat-tering factors according to Intern. Tables, Vol. C, Data cor-rections: Lorentz- and polarization factors, numerical ab-sorption correction (programs X-RED and X-SHAPE (Stoe,Darmstadt, 1994)); Reliability factor: R1/wR2 (220 reflectionswith I0>2(I)): 0.0295/0.0670, R1/wR2 (all data): 0.0338/0.0683, Goof: 1,14. Structural data: monoclinic, C2/m, Z 2, a 1078.7(4), b 522.7(1), c 739.3(2) pm, 116.45(2), V 373.2(2) A3, number of refined para-meters: 37. Further details are available at the Fachinforma-tionszentrum Karlsruhe, D-76344 Eggenstein-Leopoldshafen([email protected]) on quoting the depositorynumber CSD 413989.</p></li></ul>
Brauer Handbuch Der Prparativen Anorganischen Chemielaborante
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