Synthesis and Characterization of the Lithium-Rich Phosphidosilicates Li 10 Si 2 P 6 and Li 3 Si 3 P 7 .

The lithium phosphidosilicates Li10 Si2 P6 and Li3 Si3 P7 are obtained by high-temperature reactions of the elements or including binary Li-P precursors. Li10 Si2 P6 (P21 /n, Z = 2, a = 7.2051(4) Å, b = 6.5808(4) Å, c = 11.6405(7) Å, β = 90.580(4)°) features edge-sharing SiP4 double tetrahedra forming [Si2 P6 ]10- units with a crystal structure isotypic to Na10 Si2 P6 and Na10 Ge2 P6 . Li3 Si3 P7 (P21 /m, Z = 2, a = 6.3356(4) Å, b = 7.2198(4) Å, c = 10.6176(6) Å, β = 102.941(6)°) crystallizes in a new structure type, wherein SiP4 tetrahedra are linked via common vertices and which are further connected by polyphosphide chains to form unique∞ 2 [Si3 P7 ]3- double layers. The two-dimensional Si-P slabs that are separated by Li atoms can be regarded as three covalently linked atoms layers: a defect α-arsenic type layer of P atoms sandwiched between two defect wurzite-type Si3 P4 layers. The single crystal and powder X-ray structure solutions are supported by solid-state7 Li,29 Si, and31 P magic-angle spinning NMR measurements.