Metathesis and Redetermination of the Crystal Structure of Cadmium Carbodiimide, CdNCN

Cadmium carbodiimide, CdNCN, was synthesized by a solid‐state metathesis reaction between CdCl2 and Na2NCN in a 1 : 1 molar ratio at 500 °C, and its crystal structure was redetermined from Rietveld refinement of powder X‐ray data, aiming to clarify prior uncertainties as regards the carbodiimide vs. cyanamide shape. CdNCN adopts the centrosymmetric space group R3‾ m and is isostructural with MgNCN, the lattice parameters being a=3.536 Å and c=14.518 Å, the C−N double bond arriving at 1.23 Å. Both IR and Raman spectroscopy as well as DFT phonon calculations were carried out, and they corroborate the crystallographic result.