Li 4 Ca 3 Si 2 N 6 and Li 4 Sr 3 Si 2 N 6 – Quaternary Lithium Nitridosilicates with Isolated [Si 2 N 6 ] 10– Ions

The isotypic nitridosilicates Li 4 Ca 3 Si 2 N 6 and Li 4 Sr 3 Si 2 N 6 were synthesized by reaction of strontium or calcium with Si(NH) 2 and additional excess of Li 3 N in weld shut tantalum ampoules. The crystal structure, which has been solved by single‐crystal X‐ray diffraction (Li 4 Sr 3 Si 2 N 6 : C 2/ m , Z = 2, a = 6.1268(12), b = 9.6866(19), c = 6.2200(12) Å, β = 90.24(3)°, wR 2 = 0.0903) is made up from isolated [Si 2 N 6 ] 10– ions and is isotypic to Li 4 Sr 3 Ge 2 N 6 . The bonding angels and distances within the edge‐sharing [Si 2 N 6 ] 10– double‐tetrahedra are strongly dependent on the lewis acidity of the counterions. This finding is discussed in relation to the compounds Ca 5 Si 2 N 6 and Ba 5 Si 2 N 6 , which also exhibit isolated [Si 2 N 6 ] 10– ions.