Synthesis and Characterization of the Lithium-Rich Phosphidosilicates Li10Si2P6 and Li3Si3P7

The lithium phosphidosilicates Li 10 Si 2 P 6 and Li 3 Si 3 P 7 are obtained by high-temperature reactions of the elements or including binary Li–P precursors. Li 10 Si 2 P 6 ( P 2 1 / 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 SiP 4 double tetrahedra forming [Si 2 P 6 ] 10– units with a crystal structure isotypic to Na 10 Si 2 P 6 and Na 10 Ge 2 P 6 . Li 3 Si 3 P 7 ( P 2 1 / 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 SiP 4 tetrahedra are linked via common vertices and which are further connected by polyphosphide chains to form unique ∞ 2 [Si 3 P 7 ] 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 Si 3 P 4 layers. The single crystal and powder X-ray structure solutions are supported by solid-state 7 Li, 29 Si, and 31 P magic-angle spinning NMR measurements.