Lone-pair containment in closed cavities. The MTe6O13 (M = Mn, Ni, Co) family of ternary oxides

Abstract

The hydrothermal and ceramic syntheses, single crystal structures and some properties of MnTe₆O₁₃, NiTe₆O₁₃ and CoTe₆O₁₃ are described. These isostructural phases [space group R (No. 148) with a ≈ 10.2 Å and c ≈ 19 Å] contain a dense network of isolated MO₆ (M = Mn, Ni, Co) octahedra, TeO₄ folded squares and distorted TeO₄₊₁ square-based pyramids, sharing vertices and edges by way of M–O–Te and Te–O–Te bonds. The Te^IV lone pairs are directed into closed cavities formed from 18 Te-centred and 6 MO₆ groupings. Magnetic susceptibility data for MnTe₆O₁₃ and CoTe₆O₁₃ show antiferromagnetic ordering at ca. 13 and 21 K, respectively, which must occur via a superexchange pathway.