Sr4N[CN2][C2N]: The First Carbodiimide Acetonitriletriide

The acetonitriletriide anion C2N3-, the fully deprotonated form of acetonitrile, is stabilized in a pure alkaline earth metal environment in Sr4N[CN2][C2N]. The heterogeneous reaction of graphite and elemental nitrogen (from decomposed NaN3) with Sr2N at 1020 K yields for the first time a phase that contains the two triatomic anions acetonitriletriide C2N3- and carbodiimide CN22- side by side. Further synthetic routes were likewise successfully tested, including a sodium free approach (Sr2N + C) and the use of NaCN as carbon and nitrogen source. The monoclinic crystal structure is derived from powder and single‐crystal X‐ray diffraction data (P21/c, a = 397.74(1) pm, b = 1411.72(3) pm, c = 692.57(1) pm, v = 103.57(1)°, Z = 2). The existence of both anions in Sr4N[CN2][C2N] is further confirmed by IR and Raman spectroscopy. With its novel 1‐D chain structure of edge‐sharing NSr6 octahedra, the material also enriches the structural variety of ternary alkaline earth metal nitrides.