Stabilization of Guanidinate Anions [CN3]5−[CN_3]^{5−} in Calcite‐Type SbCN3_3

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 SbCN$_3$ at pressures of 32–38 GPa using various synthetic routes in laser-heated diamond anvil cells. SbCN$_3$, which is isostructural to calcite CaCO$_3$, can be recovered under ambient conditions. Its structure contains the previously elusive guanidinate anion $[CN_3]^{5−}$, marking a fundamental milestone in carbonitride chemistry. The crystal structure of SbCN$_3$ was solved and refined from synchrotron single-crystal X-ray diffraction data and was fully corroborated by theoretical calculations, which also predict that SbCN$_3$ 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

Unraveling the Bonding Complexity of Polyhalogen Anions: High-Pressure Synthesis of Unpredicted Sodium Chlorides Na2_2Cl3_3 and Na4_4Cl5_5 and Bromide Na4_4Br5_5

The field of polyhalogen chemistry, specifically polyhalogen anions (polyhalides), is rapidly evolving. Here, we present the synthesis of three sodium halides with unpredicted chemical compositions and structures (tP10-Na$_2$Cl$_3$, hP18-Na$_4$Cl$_5$, and hP18-Na$_4$Br$_5$), a series of isostructural cubic cP8-AX$_3$ halides (NaCl$_3$, KCl$_3$, NaBr$_3$, and KBr$_3$), and a trigonal potassium chloride (hP24-KCl$_3$). The high-pressure syntheses were realized at 41–80 GPa in diamond anvil cells laser-heated at about 2000 K. Single-crystal synchrotron X-ray diffraction (XRD) provided the first accurate structural data for the symmetric trichloride Cl3– anion in hP24-KCl3 and revealed the existence of two different types of infinite linear polyhalogen chains, [Cl]$_∞$$^{n–}$ and [Br]$_∞$$^{n–}$, in the structures of cP8-AX$_3$ compounds and in hP18-Na$_4$Cl$_5$ and hP18-Na$_4$Br$_5$. In Na$_4$Cl$_5$ and Na$_4$Br$_5$, we found unusually short, likely pressure-stabilized, contacts between sodium cations. Ab initio calculations support the analysis of structures, bonding, and properties of the studied halogenides