Sc2Te5O13 and Sc2TeO6:: The first oxotellurates of scandium

Sc2Te5O13 and Sc2TeO6 are the first oxotellurates of scandium that could be structurally elucidated by X-ray diffraction using single crystals. The scandium(III) oxotellurate(IV) Sc2Te5O13 was synthesized by reacting Sc2O3 with TeO2 at 850 degrees C and crystallizes in the triclinic system with space group P1 (no. 2) and the lattice parameters a = 660.67(5), b = 855.28(7), c = 1041.10(9) pm, alpha = 86.732(8), beta = 86.264(8), and gamma = 74.021(8)degrees (Z = 2). The crystal structure contains chains respectively strands of alternatingly edge- and vertex-sharing [ScO6](9-) and [ScO7](11-) polyhedra. These strands are connected by [TeO3+1]((2+2)-) oxotellurate(IV) anions. The coordination spheres of Sc3+ appear markedly smaller than those of M3+ cations in the other known compounds of the formula type M2Te5O13 (M = Y, Dy - Lu), therefore Sc2Te5O13 is not really isotypic, but only isopuntal with these compounds. Single crystals of the scandium(III) oxotellurate(VI) Sc2TeO6 were obtained through the fusion of a mixture Of Sc2O3 and TeO3 at 850 degrees C. It crystallizes trigonally (a = 874.06(7), e = 479.85(4) pm and c/a = 0.549) with the Na2SiF6-type structure in space group P321 (no. 150) and three formula units per unit cell. Its crystal structure is built up by a hexagonal closest packing (hcp) of oxide anions with the Sc3+ cations residing in 1/3 and the Te6+ cations in 1/6 Of the octahedral interstices in a well-ordered occupation pattern. Thus one can address the structural situation in Sc-2[TeO6] as a stuffed beta-WCl6-type arrangement.