Stabilization of Guanidinate Anions [CN₃ ]^5- in Calcite-Type SbCN₃

The stabilization of nitrogen-rich phases presents a significant chemical challenge due to the inherent stability of the dinitrogen molecule. This stabilization can be achieved by utilizing strong covalent bonds in complex anions with carbon, such as cyanide CN^- and NCN^2- carbodiimide, while more nitrogen-rich carbonitrides are hitherto unknown. Following a rational chemical design approach, we synthesized antimony guanidinate SbCN₃ at pressures of 32-38 GPa using various synthetic routes in laser-heated diamond anvil cells. SbCN₃ , which is isostructural to calcite CaCO₃ , can be recovered under ambient conditions. Its structure contains the previously elusive guanidinate anion [CN₃ ]^5- , marking a fundamental milestone in carbonitride chemistry. The crystal structure of SbCN₃ was solved and refined from synchrotron single-crystal X-ray diffraction data and was fully corroborated by theoretical calculations, which also predict that SbCN₃ has a direct band gap with the value of 2.20 eV. This study opens a straightforward route to the entire new family of inorganic nitridocarbonates.