Nitridogermanates(IV) : the germanide oxide Sr15Ge[GeN4]3O, the carbodiimide Ba5[GeN4][CN2], and the oxidonitridogermanate Sr6[Ge2N6O]

Abstract

Various novel compounds have been encountered by serendipity, due to small oxygen or carbon impurities, during the explorative studies to explore the crystal chemistry of multinary germanium nitrides and nitridogermanates. With oxygen in a closed reaction container, both the germanide nitridogermanate(IV) oxide Sr15Ge[GeN4]3O and the oxidonitridodigermanate Sr6[Ge2N6O] are observed when reacting germanium or germanium nitride in an sodium flux with strontium and nitrogen produced in situ from decomposition of sodium azide or amide. The former compound contains three different anions: germanide anions, Ge4‐, next to complex nitridogermanate(IV) ions [GeN4]8‐, and thus presents germanium in its lowest and highest possible oxidation state. Additional oxide ions are ascertained according to charge balance and distances to surrounding strontium ions. In the oxidonitridodigermanate(IV) Sr6[Ge2N6O], the oxygen rather replaces nitrogen within the nitridogermanate ion. Finally, carbon impurities under the given reaction conditions are known to preferentially react to carbodiimide ions, which are found as constituents within the novel carbodiimide nitridogermanate(IV) Ba5[GeN4][CN2], corroborated by Raman spectroscopy.