Synthesis and characterisation of the quaternary cyanamide Li2MgSn2(NCN)6.

The quaternary cyanamide Li2MgSn2(NCN)6 was prepared by a solid‐state metathesis reaction between Li2NCN, MgF2, and SnF4. Its trigonal structure was determined from powder X‐ray diffraction data to be isotypic to that of Li2MnSn2(NCN)6 with P3‾1m symmetry. The new phase is well thought of as being derived from a [NiAs]‐type MNCN structure with Sn2(NCN)32+ corundum‐like layers alternating with Li2Zr(NCN)3‐like Li2Mg(NCN)32− layers. Structural anomalies in the shape of the cyanamide units are addressed via PXRD, IR spectroscopy as well as density‐functional theory, all of them suggesting the presence of N≡C−N2− cyanamide units. [ABSTRACT FROM AUTHOR]