Zwei Fluoridborate des Gadoliniums: Gd2F3[BO3] und Gd3F3[BO3]2

Abstract

Inhaltsübersicht. Durch flußmittelunterstützte Festkörperreaktion von Gd 2 O 3 und GdF 3 mit B 2 O 3 (Flußmittel: CsCl, molares Verhältnis: 1 : 1 : 1 : 6, verschweißte Tantalampulle, 700°C, 7 d) läßt sich das neue Gadoliniumfluoridborat Gd 2 F 3 [BO 3 ] (monoklin, P2 1 /c; a ϭ 1637,2(1), b ϭ 624,78(4), c ϭ 838,04(6) pm, β ϭ 93,341(8)°; V m ϭ 64,418(6) cm 3 /mol, Z ϭ 8) in Form farbloser, flächenreicher Prismen einkristallin erhalten. Die vier kristallographisch verschiedenen Gd 3ϩ -Kationen werden darin allesamt überkappt quadratisch-antiprismatisch (CN ϭ 9) von Fluorid-und Oxid-Anionen umgeben, wobei letztere immer Bestandteil isolierter, trigonal planarer [BO 3 ] 3Ϫ -Anionen sind. Die sechs kristallographisch unabhängigen F Ϫ -Anionen liegen allesamt in mehr oder we-Abstract. By flux-supported solid-state reaction of Gd 2 O 3 and GdF 3 with B 2 O 3 (flux: CsCl, molar ratio: 1 : 1 : 1 : 6, sealed tantalum capsule, 700°C, 7 d) the new gadolinium fluoride borate Gd 2 F 3 [BO 3 ] (monoclinic, P2 1 /c; a ϭ 1637.2(1), b ϭ 624.78(4), c ϭ 838.04(6) pm, β ϭ 93.341(8)°; V m ϭ 64.418(6) cm 3 /mol, Z ϭ 8) was obtained as colourless, prismatic, face-rich single crystals. The four crystallographically different Gd 3ϩ cations (CN ϭ 9) are all capped square-antiprismatically surrounded by fluoride and oxide anions, in which the latter represent always components of isolated trigonal planar [BO 3 ] 3Ϫ anions. The six crystallographically independent F Ϫ anions all reside in more or less planar coordination of three Gd 3ϩ cations. Thus the constitution of Gd 2 F 3 [BO 3 ] can be described as Einleitung Während die Zweistoffsysteme B 2 O 3 / M 2 O 3 (M ϭ Sc, Y, La; Ce Ϫ Lu) bereits ausführlich untersucht wurden [1Ϫ4], ist über anionisch derivatisierte Oxoborate der dreiwertigen Selten-Erd-Elemente fast nichts bekannt. Sieke [5] (und in Fortsetzung davon Nikelski [6]) beschreiben zwar den Einbau von Chlorid-Anionen in Lanthanidborate, so daß mit der Kenntnis um die Zusammensetzung und den strukturellen Aufbau von Ce 3 Cl 3 [BO 3 ] [7], PrCl(BO 2 ) 2 [8] und Er 2 Cl 2 [B 2 O 5 ] [9] wenigstens auf diesem Gebiet ein gewisser

High-pressure Syntheses and Characterization of the Rare-earth Fluoride Borates RE2(BO3)F3 (RE=Tb, Dy, Ho)

“…According to the systematic extinctions, the monoclinic space group P2 1 /c was derived for the three isotypic compounds. Due to the fact that the compounds RE 2 (BO 3 )F 3 (RE = Tb, Dy, Ho) are isotypic to Gd 2 (BO 3 )F 3 [4], the structural refinement was performed using the positional parameters of Gd 2 (BO 3 )F 3 as starting values (SHELXL-97 [15,16] (full-matrix least-squares on F 2 )). All rare-earth atoms and most of the anions were refined with anisotropic displacement parameters.…”

“…In 2002, Müller-Bunz et al tried to reproduce the synthesis of Gd 3 (BO 3 ) 2 F 3 without success. All their attempts led to the rareearth fluoride borate Gd 2 (BO 3 )F 3 [4], which is structurally related. Müller-Bunz et al yielded single crystals with sufficient quality for a single-crystal structure determination.…”

Synthesis of Er5(BO3)2F9 and Properties of RE5(BO3)2F9 (RE = Er, Yb)

“…The arrangement can be described via alternating layers of the formal compositions "ErBO 3 " and "ErF 3 ", spreading into the bc-plane. For a more detailed description of the structure, including a comparison to the related structures of RE 3 (BO 3 ) 2 F 3 (RE = Sm, Eu, Gd) [5] and Gd 2 (BO 3 )F 3 [6], the reader is referred to the description of the isotypic compound Yb 5 (BO 3 ) 2 F 9 (ref. [1]).…”

“…Before we started our high-pressure / high-temperature research, rare-earth fluorido-and fluoride borates were only represented by the compounds RE 3 (BO 3 ) 2 F 3 (RE = Sm, Eu, Gd) [4] and Gd 2 (BO 3 )F 3 [5], synthesized by heating a stoichiometric mixture of RE 2 O 3 , B 2 O 3 , and REF 3 under ambient pressure conditions. There is a close relationship between these two structure-types and the recently discovered high-pressure ytterbium fluoride borate Yb 5 (BO 3 ) 2 F 9 [1].…”

High-pressure Synthesis and Characterization of the Rare-earth Fluoride Borate LaB2O4F

“…Due to the high flexibility of the BO 3 and BO 4 groups to form structures with isolated BO 3 and BO 4 groups, discrete groups (e. g. [B 3 O 6 ] 3− ), chains, layers, or complicated networks via the linkage of the corners of the groups or via edge-sharing of BO 4 tetrahedra, it is more than likely that a large number of new compounds with interesting properties can be expected in the future. At the beginning of our research in the field of fluoride borates, the system RE-B-O-F was only represented by the rare-earth fluoride borates RE 3 (BO 3 ) 2 F 3 (RE = Sm, Eu, Gd) [2,3] and Gd 2 (BO 3 )F 3 [4]. These compounds were synthesized under ambient-pressure conditions by heating stoichiometric mixtures of RE 2 O 3 , B 2 O 3 and REF 3 .…”