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

Abstract

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 R (Formula presented.) 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.