A Fluorooxosilicophosphate with an Unprecedented SiO2 F4 Species.

The large number and structural beauty of silicates are largely due to the variety of connection mode of SiO4 tetrahedra. SiO6 and SiF6 octahedra are also known and give rise for structural versatility of inorganic silicates. However, to date, the crystal structure of inorganic fluorooxosilicates with oxofluoride SiOx F4-x or SiOx F6-x species are unknown. Now, fluorine was successfully introduced into the silicophosphates, and the first fluorooxosilicophosphate K4 Si3 P2 O7 F12 with an unprecedented SiO2 F4 species was synthesized. The existence of Si-F bonds was verified by comprehensively experimental and theoretical work. Using ab initio and bond valence calculations, the oxofluoride SiOx F6-x species is shown to be stable when oxygen atoms connect to other atoms with strong covalent interactions. This work will contribute to the structural diversity of silicate chemistry by the exploration of the new fluorooxosilicates.