Ruby-red, bead-shaped single crystals of C-type La 2 Se 3 (a = 905.21(6) pm), Pr 2 Se 3 (a = 891.17(6) pm), and Gd 2 Se 3 (a = 872.56(5) pm) are obtained by oxidation of the respective rare-earth metal (M = La, Pr and Gd) with selenium (molar ratio 2 : 3) in evacuated silica tubes at 750°C in the presence of fluxing CsCl within seven days. Their crystal structure belongs to a cation-deficient Th 3 P 4 -type variant (cubic, I 4 3d) according to M 2.667 & 0.333 Se 4 (Z = 4) or M 2 Se 3 (Z = 5.333) offering coordination numbers of eight (Se 2± ar-ranged as trigonal dodecahedra) to the M 3+ cations. In spite of the high Cs + activity in molten CsCl, no cesium incorporation into the M 5.333 & 0.667 Se 8 -frame structure (e. g. as CsM 5 Se 8 with Z = 2) could be achieved, judged from both results of electron beam X-ray microanalyses and refined occupation factors of the metal position very close to x = 8/9 for M 3x Se 4 .
The oxidation of most of the lanthanide dihydrides MH2 (M = LaNd; GdEr, Lu) with equimolar amounts of selenium results in the formation of the first lanthanide hydride selenides MHSe. The presence of alkali chlorides (e.g., NaCl or CsCl) as fluxes secures complete and fast reactions (7 d) at 700–850°C in sealed, arc‐welded tantalum capsules (protected by evacuated silica vessels) as well as single‐crystalline products (pale bluish‐gray hexagonal columns or platelets). Two different structures were determined from X‐ray single crystal data for the examples of 2HCeHSe (hexagonal, P63/mmc (no. 194), Z = 2, a = 406.36(4), c = 794.81(9) pm, R1 = 0.0365, wR2 = 0.0766) and 1HHoHSe (hexagonal, P6m2 (no. 187), Z = 1, a = 381.56(3), c = 387.28(5) pm, R1 = 0.0140, wR2 = 0.0337). According to X‐ray powder data, the hydride selenides MHSe with M = LaNd proved to be isostructural with 2H‐CeHSe, those with M = GdEr and Lu crystallize isotypically with 1HHoHSe just like YHSe. Both structures contain hydrogen in half of the trigonal planar interstices within closest‐packed mono‐layers of the metals. These layers ∞2[(M3+)(H−)3/3]2+ (a,β or b,α) are alternatively sheethed with closest‐packed mono‐layers of Se2− (C) along [001], and only the stacking sequence decides whether a “stuffed” WC‐ (C(a,β)C 1 H‐MHSe) or a “stuffed” anti‐NiAs‐type arrangement (C(a,β)C(b,α)C 2HMHSe) emerges.
Einkristalle von Lanthanoid‐Sesquiseleniden (M2Se3; hier: M = Ce, Gd, Lu) gewinnt man bei der Umsetzung der Elemente (Lanthanoid und Selen) im molaren Verhältnis von 2:3 innerhalb von sieben Tagen bei 850 °C in evakuierten Quarzglasampullen, wenn äquimolare Mengen an NaCl als Flußmittel zugegen sind. Im Falle von Ce2Se3 (a = 897, 74(6) pm) und Gd2Se3 (a = 872, 56(5) pm) entsteht der kubische C‐Typ (I4¯3d, Z = 5, 333) in Form von dunkelroten Perlen, für Lu2Se3 (a = 1125, 1(1); b = 798, 06(8); c = 2387, 7(2) pm) der orthorhombische Z‐Typ (Fddd, Z = 16) als orangegelbe Quader. Bei der Oxidation von Monochlorid‐Hydriden (MClHx bzw. AyMClHx; M = Ce, Gd, Lu; x = 1; A = Li, Na; y = 0, 5) mit Selen werden aus verschweißten Tantal‐Ampullen mit C‐Ce2Se3 und Z‐Lu2Se3 die gleichen Hauptprodukte erhalten, selbst wenn Überschüsse an NaCl bzw. LiCl als Flußmittel zum Einsatz kommen. Im Falle von Gd2Se3 bilden sich dagegen schwarzrote Nadeln vom orthorhombischen U‐Typ (Pnma, Z = 4; a = 1118, 2(1); b = 403, 48(4); c = 1097, 1(1) pm) an Stelle von C‐Gd2Se3. C‐Ce2Se3 kristallisiert gemäß Ce2, 667□0, 333Se4 mit Z = 4 in einer kationendefekten Th3P4‐Struktur (Ce2S3‐Typ) mit Z = 5, 333 für die Formel Ce2Se3. Ce3+ ist hier von acht Se2—‐Anionen trigondodekaedrisch koordiniert. In U‐Gd2Se3 (U2S3‐Typ) liegen zwei kristallographisch unterschiedliche Gd3+‐Kationen mit Koordinationszahlen von 7 (Gd1) bzw. 7+1 (Gd2) und ein‐ bzw. zweifach überkappten trigonalen Prismen als Koordinationspolyedern vor. Auch Z‐Lu2Se3 (Sc2S3‐Typ) weist zwei verschiedene Lu3+‐Kationen auf, die sich jedoch beide in oktaedrischer Sechser‐Koordination der Se2—‐Anionen befinden.
The synthesis and crystal structure of a series of rare earth metal hydride tellurides with the composition REHTe (RE = Y, La–Nd, Gd–Er) is reported. These compounds have been obtained by the reaction of rare earth metal dihydrides (REH2) with elemental tellurium in sealed tantalum capsules at T = 700°C using cesium chloride (CsCl) as fluxing agent, which can be washed away with water due to the astonishing insensitivity of these hydride tellurides (REHTe) against hydrolysis. All of the compounds crystallize in the hexagonal space group P6̅m2 with a filled WC-type crystal structure, exhibiting a mutual trigonal-prismatic coordination of the heavy ions (RE3+ and Te2−), while the hydride anions reside in the trigonal prismatic voids surrounded by three rare earth metal cations expanding their coordination pattern to a tricapped trigonal prism. This 1H-type crystal structure is compared with the 1H- and 2H-type structures of the respective hydride selenides (REHSe, RE = Y, La–Nd, Gd–Tm, Lu). Both hexagonal basic crystal structures can be derived from the AlB2-type structure as demonstrated in a Bärnighausen tree by group-subgroup relationships.
Synthesis and Crystal Structure of Cs3Y7Se12 The oxidation of yttrium metal with selenium in the presence of CsCl (7 d, 700°C, evacuated silicia tubes) results in the formation of pale yellow, lath‐shaped single crystals of Cs3Y7Se12. The crystal structure (orthorhombic, Pnnm, Z = 2, a = 1272.8(3), b = 2627.7(5), c = 413.32(8) pm) consists of edge‐ and vertex‐connected [YSe6] octahedra forming a rocksalt‐related network [Y7Se12]3−. One‐dimensional infinite channels along [001], apt to take up extra cations, provide coordination numbers of 6 and 7 + 1, respectively, for two crystallographically different Cs+.
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