Mixed‐Valent Europium in the Cubic Thiosilicate Li 3 Eu 6 [SiS 4 ] 4

In an attempt to synthesize LiEu 3 S 3 [SiS 4 ] utilizing elemental europium and sulfur as well as SiS 2 and an excess of LiCl as flux and lithium source, dark red, platelet‐shaped single crystals of Li 3 Eu 6 [SiS 4 ] 4 were obtained. This new compound crystallizes in the cubic space group I 4 3 d ( a = 1369.22(5) pm) with four formula units per unit cell. Both the Li + and the Si 4+ cations are surrounded by four sulfide anions. The [SiS 4 ] 4– tetrahedra show merely a slight trigonal distortion, while the [LiS 4 ] 7– units are best described as flattened bisphenoids. The europium cations exhibit an eightfold, rather irregular coordination environment by eight S 2– anions and have to be regarded mixed‐valent with a +2:+3 charge‐ratio of 5:1 in order to gain electroneutrality. The lack of an inversion center is caused by the [SiS 4 ] 4– tetrahedra being stacked exclusively top up along [111] in this acentric crystal structure.