Ca3Sm3[Si9N17] and Ca3Yb3[Si9N17] Nitridosilicates with Interpenetrating Nets that Consist of Star-Shaped [N[4](SiN3)4] Units and [Si5N16] Supertetrahedra

Abstract New nitridosilicates Ca3Sm3[Si9N17] and Ca3Yb3[Si9N17] were synthesized from the reactions of the pure metals (calcium and samarium/ytterbium) with silicon diimide “Si(NH)2” in a radio-frequency (rf) furnace at temperatures of up to 1650 °C. These isotypic compounds crystallize in the cubic space group Pbar 43m (no. 215) with lattice parameters a=739.50(3) pm; V=0.4044(1) nm3; Z=1; wR2=0.029 (240 diffraction data, 26 parameters) for Ca3Sm3[Si9N17] and a=730.20(2) pm; V=0.3893(1) nm3; wR2=0.039 (387 diffraction data, 27 parameters) for Ca3Yb3[Si9N17]. The new structure type of Ca3RE3[Si9N17] (RE=Sm, Yb) consists of two independent infinite networks, each of which have an expanded sphalerite (ZnS) topology in which the positions of the Zn and S atoms are replaced by voluminous [N[4](SiN3)4] units and [Si5N16] supertetrahedra, respectively, thereby displaying twofold interpenetration. As well, a structural description of Ca3Yb3[Si9N17], its thermal stability, and magnetic properties, as well as UV/Vis, IR, and Raman spectra, are presented.