The Unique Crystal Structure of the Triclinic Samarium(III) Oxoselenate(IV) Sm2[SeO3]3

Das Ytterbium(III)-Oxidbromid-Oxidotellurat(IV) Yb3O2Br[TeO3]2

The ytterbium(III) oxide bromide oxidotellu-rate(IV) Yb3O2Br[TeO3]2 was obtained from a mixture of Yb2O3, YbBr3 and TeO2 in a molar ratio of 2:1:2 along with an excess of KBr as fluxing agent in evacuated fused silica ampoules after 10 days at T = 800 °C and subsequent slow cooling to room temperatures as colorless, plate-shaped single crystals. Its triclinic crystal structure (a = 663.97(5), b = 697.46(5), c = 1080.15(8) pm, α = 105.102(3), β = 90.931(3), γ = 100.034(3)°; Z = 2, space group: P 1 ‾ $‾{1}$ ) displays three crystallographically different Yb3+ cations with coordination numbers of six, seven and eight. Six out of eight distinct oxygen atoms belong to two independent ψ1-tetrahedral [TeO3]2−anions, whereas the other two represent O2− anions in tetrahedral coordination of four Yb3+ cations each, not having any contact to tellurium. Condensed via common vertices and edges, these [OYb4]10+ tetrahedra form cationic layers ∞ 2 ${}_{\infty }{}^{2}$ {[O2Yb3]5+}, which spread out parallel to the (001) plane. Two discrete [TeO3]2− groups and one Br− anion per formula unit take care of their three-dimensional interconnection along [001] and the overall charge balance of Yb3O2Br[TeO3]2. Remarkable interactions between the lone pair of electrons at the Te4+ cations of the ψ1-tetrahedral [TeO3]2− anions and those at the Br− anions are discussed.

The complete series of sodium rare-earth metal(III) chloride oxotellurates(IV) Na2 RE 3Cl3[TeO3]4 (RE = Y, La–Nd, Sm–Lu)

The complete series of sodium rare-earth metal(III) chloride oxotellurates(IV) with the composition Na2 RE 3Cl3[TeO3]4 (RE = Y, La–Nd, Sm–Lu) has been synthesized via solid-state reactions. For these conversions mixtures of the respective rare-earth metal(III) oxides, tellurium dioxide and sodium chloride as flux and reactant were prepared, intimately ground and heated for 5 days at 1225 K. The almost colorless single crystals were characterized via single-crystal X-ray diffractometry. In the monoclinic crystal structure of these compounds two crystallographically different rare-earth metal(III), but only one sodium cation sites occur. [REO8]13− polyhedra around both RE 3+ positions as well as sodium-centered polyhedra [NaO4Cl4]8− form layers via different connectivity modes. These layers spread out parallel to the (001) plane and arrange alternatingly resulting in the three-dimensional network of the Na2 RE 3Cl3[TeO3]4 structure, where the Te4+ lone-pair cations at two different sites work as linkers by forming isolated ψ 1-tetrahedra [TeO3]2−. Some of these compounds were represented before in different settings of space group C2/c. Now the complete series of the Na2 RE 3Cl3[TeO3]4 representatives with RE = Y, La–Nd, Sm–Lu is described consistently for a better comparison and understanding. Additionally, a single crystal of Na2Pr3Cl3[TeO3]4 was measured via energy dispersive X-ray analysis to verify the included elements, powder samples of Na2Nd3Cl3[TeO3]4 were characterized by X-ray diffractometer data for a phase-purity check and a single-crystal Raman spectrum of Na2Yb3Cl3[TeO3]4 served for proving the signature of discrete [TeO3]2− anions.

Die Lanthanoid(III)-Oxid-Oxoselenate(IV) Ln 2O[SeO3]2 (Ln=Sm–Tm)

Single crystals of compounds with the composition Ln 2O[SeO3]2 (Ln=Sm–Tm) were synthesized by solid-state reactions of the lanthanoid sesquioxides (Ln 2O3) with the corresponding tribromides (LnBr3) and selenium dioxide (SeO2) in a molar ratio of 2:1:2 in evacuated torch-sealed silica ampoules. For the terbium case, Tb4O7 and SeO2 have been reacted with elemental Tb in a molar ratio of 3:14:2. These lanthanoid(III) oxide oxoselenates(IV) all crystallize tetragonally with the space group P42/ncm and decreasing lattice parameters from the lighter to the heavier Ln 3+ cations (from a=1077.03(8) pm and c=526.38(4) pm for Ln=Sm to a=1049.60(8) pm and c=516.04(4) pm for Ln=Tm) according to the lanthanide contraction. They show a three-dimensional network of condensed [LnO8]13− polyhedra with a channel structure, where all ψ 1-tetrahedral [SeO3]2− units are coordinating with their O2− anions to square antiprisms [LnO8]13− and pointing with their non-bonding electron pairs into the empty channels, which propagate along [001]. As another characteristic feature of the crystal structure, [OLn 4]10+ tetrahedra containing the non-selenium-bonded O2− anions are trans-edge-connected to form {[O L n 4 / 2 e ] 4 + } ∞ 1 ${}_\infty ^{\rm{1}}{\rm{\{ [O}}Ln_{4/2}^{\rm{e}}{{\rm{]}}^{{\rm{4}} + }}{\rm{\} }}$ chains, which run parallel to the lone-pair channels in [001] direction and build up a tetragonal rod-packing.