| Abstract: | On the Structure of Sr3(BN2)2 The structure of Sr3(BN2)2 was determined on single-crystal X-ray data collected with a four-circle diffractometer. Sr3(BN2)2 crystallizes in the cubic space group Im3 m (no. 229) with a = 764.56(3) pm and Z = 3. The structure contains linear BN3?2 ions with a B? N bond length of 135.8(6) pm. The straight forward synthesis employing metal nitrides plus boron nitride yielded crystalline powders of M3(BN2)2 (M = Ca, Sr) at 1100°C (5 days). Cubic indexing of guinier patterns gave a = 765.8(1) pm for M = Sr and a = 734.7(2) pm for M = Ca. The structure refinement on a single crystal of Sr3(BN2)2 revealed that one strontium site (2a; 0, 0, 0) is occupied by only about 50%. It has been tried to fully occupy this site with an alkali metal (A) to obtain ASr4(BN2)3 (Z = 2). Reactions with A = Na yielded crystalline powders. Cubic indexing of the guinier pattern analogous to that of Sr3(BN2)2 gave a = 754.2(1) pm. |
