Syntheses, crystal structures, and vibrational spectroscopic properties of MgCN2, SrCN2, and BaCN2

The alkaline-earth metal cyanamides MgCN* SrCN* and BaCN 2 were prepared by the reaction of melamine with the metal nitrides (M&N2, Sr-jN, Ba 3 N 2 ) at temperatures between 740 e C and 850 °C. MgCN 2 was structurally characterized by X-ray analysis using powder methods (R3m, Ζ 3 , a=327.34(1) pm, c-1412.82(5) pm). The crystal structures of S r C N 2 and BaCN 2 were determined from X-ray single crystal data (SrCN 2 : Pnma, Ζ-A, 0-1241.0(2) pm, 6-396.3(2) pm, c-538.9(2) pm, BaCN 2 : R3c, Z=18, e-1528.2(2) pm, c-70l.3(2) pm). All compounds consist of the respective cations and CN2 ~-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.