Synthesis, Crystal Structure, and Chemical Bonding of Ba2SiP4

Abstract

Ba2SiP4 was synthesized by heating of the elements at 1173 K and the crystal structure was determined from single-crystal X-ray diffraction [I42d, a = 990.57(3) pm, c = 731.80(3) pm; Z = 4]. The novel structure is homeotypic to hp-Zn2SiO4 but the SiP4 tetrahedra are exclusively bridged by P–P bonds [d(P–P) = 222 pm] which is hitherto unprecedented. The three-dimensional SiP4 network is analogous to β-cristobalite if oxygen is formally replaced by a P–P dimer. Barium fills the voids and is coordinated by eight phosphorus atoms. DFT calculations indicate covalent Si–P and P–P bonding and an indirect energy gap of ca. 1 eV.