Oxotellurate(IV) der Lanthanide: I. Die isotype Reihe M₂Te₄O₁₁ (M = La – Nd, Sm – Yb)

Abstract

The present work is the first comprehensive account of the knowledge acquired from single crystals of the isotopic series M 2 Te 4 O 11 (M = La -Nd, Sm -Yb). In the crystal structure, the M 3+ cation is coordinated by eight oxygen atoms in the shape of a distorted square antiprism. Out of these polyhedra a mesh-like [M 2 O 16 ] 14− layer parallel to the (001) plane is built via three common edges. The [Te 4 O 11 ] 6− double layers in turn build two tellurium-oxygen chains crosswise to each other. The construction of the tellurium-oxygen partial structure is, however, only possible taking the secondary Te-O contacts into consideration. In most oxotellurates(IV), three oxygen atoms are covalently bound to the Te atoms (d(Te-O) ≈ 180 − 200 pm; ψ 1 tetrahedron). Another oxygen atom is found in the near vicinity at a distance of 230 to 280 pm. The significance of such secondary interactions for the stability of the crystal structures was recognized recently in theoretical as well as experimental investigations. All oxygen atoms with distances smaller than 280 pm are counted to the secondary coordination sphere. This limit may seem somewhat arbitrary but it accounts very well for the Te-O partial structure. The coordination sphere for the tellurium center is a ψ 1 trigonal bipyramid including the stereochemically active electron pair ("lone pair"). A description of the crystal structure is also possible without this partial structure, however in the [TeO 3+1 ] 4− polyhedra above and below the meshes of [M 2 O 10 ] 14− layers are linked via Te 2 -O 6 -Te 2 contacts only.

New vanadium(IV) and titanium(IV) oxyfluorotellurates(IV): V2Te2O7F2and TiTeO3F2

“…Bridging [Te 2 O 5 ] units are also described in M 2 Te 4 O 11 (M = Lu, Y, La-Nd and Sm-Yb) (Hö ss et al, 2005;Castro et al, 1990;Weber et al, 2001;Ijjaali et al, 2003;Meier & Schleid, 2004;Shen & Mao, 2004). However, in Lu 2 Te 4 O 11 , for example, the Te-O-Te bridge angle (138.9 ) is significantly smaller than in either TiTeO 3 F 2 or V 2 Te 2 O 7 F 2 , and the [Te 2 O 5 ] units connect layers of edge-sharing LuO 8 polyhedra instead of chains of edge-sharing VO 4 F 2 octahedra.…”

Oxotellurate(IV) der Lanthanide: II. Die isotype Reihe M2Te5O13 (M = Dy – Lu) / Oxotellurates(IV) of Lanthanides: II. The Isotypic Series M2Te5O13 (M = Dy – Lu)

“…x/a 0,0605 (6) 0,0626 (5) 0,0647 (6) 0,0647 (6) 0,0660 (6) 0,0690 ( (11) 228 (7) 235 (9) 225 (10) 238 (9) 228 (8) Brought to you by | University of Arizona Authenticated Download Date | 7/23/15 1:39 PM …”

“…Statt dessen bilden sich hierbei ausschließlich die M 2 Te 4 O 11 -Vertreter [4 -11], die somit gegenüber M 2 Te 5 O 13 die wohl bevorzugten Verbindungen zu sein scheinen. Da sich für die Oxotellurate(IV) vom Formeltyp M 2 Te 4 O 11 (M = La -Nd, Sm -Yb; Ausnahme: Lu [11]) [8] vor allem die Ver-0932-0776 / 05 / 0700-0720 $ 06.00 c 2005 Verlag der Zeitschrift für Naturforschung, Tübingen · http://znaturforsch.com treter des vorderen Bereiches der leichten Lanthaniden als sehr gut zugänglich erwiesen haben, stellte sich zwanglos die Frage, ob die Existenzgrenze der neuen Zusammensetzung (M 2 Te 5 O 13 ) nun von Ho 2 Te 5 O 13 [1,2] aus auch bis an die beiden Enden des Bereiches der 4f-Elemente ausgeweitet werden könnte. In Richtung der schwereren Lanthanide (M = Er -Lu) konnte dieses Vorhaben verwirklicht werden, in Richtung des Lanthans gelang die Ausweitung des Existenzbereiches jedoch nur noch bis hin zum direkten leichteren Nachbarn des Holmiums, nämlich für Dy 2 Te 5 O 13 .…”

New Crystal Structures of Rare‐Earth Metal(III) Oxotellurates(IV) RE2Te3O9: A1‐Type (RE=La, Ce) and A2‐Type (RE=Pr, Nd)

“…They are known with different compositions depending on the molar ratio RE 2 O 3 :TeO 2 , and their general formula can thus be described as RE 2 O 3 (TeO 2 ) n . Up to now many tellurium‐dioxide rich compounds, namely RE 2 Te 4 O 11 ( n =4; RE =Sc, Y, La−Lu) [19–27] and RE 2 Te 5 O 13 ( n =5; RE =Sc, Y, Dy−Lu), [26–30] have been structurally characterized. In contrast, for the composition RE 2 Te 3 O 9 ( n =3) rather few representatives are known so far and with n =2, only Pr 2 Te 2 O 7 was reported, which contains oxygen atoms not bonded to any Te 4+ cation according to Pr 2 O[TeO 3 ] 2 [31] .…”