Synthesis and Characterization of the Ternary Carbodiimide Na ₂ Hf(NCN) ₃

Na 2 Hf(NCN) 3 was prepared via a solid‐state metathesis reaction between Na 2 NCN and HfCl 4 . Its crystal structure was determined from powder X‐ray diffraction data and found to crystallize in a low‐symmetry variant of the [NiAs] type with space group . It may, therefore, be described as a hexagonally close‐packed array of NCN 2− dianions orientated along the c ‐axis, with metal cations occupying the octahedral voids in an ordered fashion. Rietveld analysis reveals a site mixing between sodium at the 12 c site and hafnium at the 6 b site in the order of 12(1)%. Moreover, both IR measurements and density functional theory calculations are consistent with a bent carbodiimide, presumably in order to accommodate metals with considerable differences in size within the same layer. The experimental optical band gap was measured to 4.1 eV coherent with the white colored sample.