SYNTHESES, CRYSTAL-STRUCTURES, AND VIBRATIONAL SPECTROSCOPIC PROPERTIES OF MGCN2, SRCN2, AND BACN2

The alkaline-earth metal cyanamides MgCN2, SrCN2, and BaCN2 were prepared by the reaction of melamine with the metal nitrides (Mg3N2, Sr2N, Ba3N2) at temperatures between 740-degrees-C and 850-degrees-C. MgCN2 was structurally characterized by X-ray analysis using powder methods (R3mBAR, Z = 3, a = 327.34(1) pm, c = 1412.82(5) pm). The crystal structures of SrCN2 and BaCN2 were determined from X-ray single crystal data (SrCN2: Pnma, Z = 4, a = 1241.0(2) pm, b = 396.3(2) pm, c = 538.9(2) pm, BaCN2: R3cBAR, Z = 18, a = 1528.2(2) pm, c = 701.3(2) pm). All compounds consist of the respective cations and CN22--anions with an increasing degree of distortion of the coordination polyhedra with increasing radii of the cations. The structural features are correlated with vibrational spectroscopic data.