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

Abstract

The new rare‐earth metal(III) oxotellurates(IV) RE2Te3O9 (RE=La−Nd) of the so far unknown A‐type structure can be obtained as needle‐shaped single crystals through solid‐state reactions of the corresponding binary oxides. Their crystal structures were determined as A1‐type for RE=La and Ce or A2‐type for RE=Pr and Nd by single‐crystal X‐ray diffraction. Both structure types crystallize in the monoclinic crystal system, but in two different non‐centrosymmetric space groups: the A1‐type with Z=8 in space group P21 (La2Te3O9: a=569.54(3), b=2230.12(13), c=1464.71(4) pm, β=101.205(3)°; Ce2Te3O9: a=567.02(3), b=2222.61(13), c=1457.13(9) pm, β=101.134(3)°) or the A2‐type with Z=16 in space group Cc (Pr2Te3O9: a=2838.61(16), b=563.89(3), c=2522.08(15) pm, β=118.816(3)°; Nd2Te3O9: a=2826.38(16), b=561.47(3), c=2511.94(15) pm, β=118.841(3)°). In spite of the differences in the unit‐cell parameters and the symmetry, both structures consist of quite similar fundamental building blocks (FBBs) consisting of eight crystallographically distinct rare‐earth metal‐oxygen polyhedra with C.N.(RE3+) from seven to nine and always twelve different ψ1‐tetrahedral oxotellurate(IV) anions [TeO3]2−, which show a high number of secondary bonding interactions (SBIs) with each other in all four cases.

First ternary tungsten tellurate(iv) WTe2O7 with unique crystal structure type

“…These Te 4+ ⋯O 2− interactions are common in rare-earth metal(III) oxotellurates (IV) such as RE 2 Te 3 O 9 (RE = La, Ce, Pr, Nd) in a space region of d (Te⋯O) = 250-297 pm. 32 33 and the bonding interactions originate from the hyperconjugation of a σ*-Te-O molecular orbital with a non-bonded p-orbital of an oxygen atom. 34 Another common name for this specific interaction is called "chalcogen bonding".…”

“…These Te 4+ ⋯O 2− interactions are common in rare-earth metal( iii ) oxotellurates( iv ) such as RE 2 Te 3 O 9 (RE = La, Ce, Pr, Nd) in a space region of d (Te⋯O) = 250–297 pm. 32 Oxotellurate( iv ) groups, and in particular the Ψ-bisphenoidal [TeO 4 ] 4− groups, are known for their pronounced Te 4+ ⋯O 2− interactions to other [TeO 4 ] 4− groups as well as [W 2 O 10 ] 8− octahedral dimers in WTe 2 O 7 . The theoretical concept of SBIs was established by Alcock et al , 33 and the bonding interactions originate from the hyperconjugation of a σ*-Te–O molecular orbital with a non-bonded p-orbital of an oxygen atom.…”