Er2S[SiO4]: Ein Erbiumsulfid‐ortho‐Oxosilicat mit ungewöhnlicher Sulfidionen‐Koordination

During the reaction of cadmium sulfide with erbium and sulfur in evacuated silica ampoules pink lath‐shaped crystals of Er₂SSiO₄] occur as by‐product which were characterized by X‐ray single crystal structure analysis. The title compound crystallizes orthorhombically in the space group Cmce (a = 1070.02(8), b = 1235.48(9), c = 683.64(6) pm) with eight formula units per unit cell. Besides isolated ortho‐oxosilicate units SiO₄]^4?, the crystal structure contains two crystallographically independent Er³⁺ cations which are both eightfold coordinated by six oxygen and two sulfur atoms. The sulfide anions are surrounded by four erbium cations each in the shape of very distorted tetrahedra. These excentric SEr₄]¹⁰⁺ tetrahedra build up layers according to by vertex‐ and edge‐connection. They are piled parallel to (010) and separated by the isolated ortho‐oxosilicate tetrahedra.