The [NCN]2– Carbodiimide Complex Anion and Its Compounds–A “Divalent Nitride” Unit for Nitridocarbonates in Materials and Applications

Synthetic strategies guided by quantum chemistry eventually leading to inorganic nitridocarbonates containing the NCN2– complex carbodiimide anion are presented, showing the power of rational approaches in obtaining chemically tailored carbodiimides with exciting materials properties. In addition, we showcase various exemplary compounds and their attributes containing either the carbodiimide [N═C═N]2– or the cyanamide [N≡C–N]2– anion. Infrared, Raman, NMR, Mößbauer and other spectroscopies, in addition to density-functional theory, are discussed, and we also highlight future perspectives of carbodiimide chemistry by focusing on their magnetic, catalytic, and electrochemical behavior, a consequence of their oxide-analogous but more covalent bonding.