Crystal Structure of [Sr(SeC ₂ H) ₂ (NH ₃ ) ₂ ], Solved and Refined From Powder X‐Ray Diffraction Data

[Sr(SeC 2 H) 2 (NH 3 ) 2 ] was synthesized by reaction of Sr(C 2 H) 2 with red selenium in liquid ammonia using a 1:2 ratio. After evaporation of the ammonia, brownish powders were obtained showing only a moderate crystallinity compared to the alkali metal analogues. IR/Raman spectroscopic investigations confirmed the existence of – SeC 2 H anions and ammonia molecules within the crystal structure of [Sr(SeC 2 H) 2 (NH 3 ) 2 ]. Upon hydrolysis, acetylene was released as proven by gas chromatography (GC). Due to the high sensitivity of the title compound against release of NH 3 , transportation of the material to a synchrotron source failed so that the structure solution and refinement had to be carried out on powder X‐ray diffraction data (PXRD) of only moderate quality. [Sr(SeC 2 H) 2 (NH 3 ) 2 ] crystallizes in the orthorhombic space group Pnma (no. 62) with Z = 4 ( a = 15.110(2) Å, b = 9.426(2) Å, c = 7.014(1powder) Å). It represents the first compound with the recently discovered – SeC 2 H anion that does not contain charge compensating alkali metal cations. Thermal analysis (DSC/TGA) confirms release of ammonia at ambient conditions and further NH 3 molecules starting at ∼100°C. Heating to higher temperatures leads to the release of acetylene at ≈200°C and the formation of SrSe as the final product as confirmed by PXRD. Attempts to synthesize the calcium and barium congeners led to powders with even lower crystallinity. Nonetheless, IR/Raman spectroscopic investigations clearly confirm the existence of – SeC 2 H anions in these compounds as well. The calcium compound seems to contain ammonia like the strontium congener, whereas the barium compound is obviously obtained as ammonia‐free Ba(SeC 2 H) 2 . Notably, it shows a high shock sensitivity decomposing explosively.