Two New Cesium Thiotellurates: Cs 2 [TeS 2 ] and Cs 2 [TeS 3 ]

Thermal decomposition of cesium azide (CsN 3 ) leaves elemental cesium behind, which was in‐situ produced and used for the syntheses of the two new cesium thiotellurates Cs 2 [TeS 2 ] and Cs 2 [TeS 3 ] along with appropriate amounts of tellurium and sulfur. The first compound crystallizes orthorhombically in space group Cmc 2 1 with the lattice parameters a = 783.39(4), b = 1126.72(8), c = 823.04(5) pm ( Z = 4) and the second one monoclinically in space group P 2 1 / n with the lattice parameters a = 997.12(6), b = 1269.71(8), c = 1410.23(9) pm, β = 91.218(3)° ( Z = 8). While ψ 1 ‐tetrahedral complex thiotellurate(IV) anions [TeS 3 ] 2– are found as pyramids in Cs 2 [TeS 3 ], Cs 2 [TeS 2 ] comprises ψ 2 ‐tetrahedral thiotellurate(II) units [TeS 2 ] 2– as boomerangs and both occur isolated in the corresponding structures. In each of the title compounds, the anionic part of the structures is arranged layer‐like with Cs + cations sitting in between the layers. The cesium cations in the sulfur‐rich compound Cs 2 [TeS 3 ] exhibit coordination numbers of seven and eight, while in the Cs 2 [TeS 2 ] these cations are surrounded by only six sulfide anions. But even the lone‐pair electrons at the central Te 4+ and Te 2+ cations help to complete the Cs + coordination spheres in both cases.